This is a breakdown of my methodology for calculating the optimal mix of gear for the Seer Sage and Corruption Sorcerer--"Showing my work" for public/peer review, if you will.

Foreward:

I have been, since 2015, writing and updating/maintaining a complete guide to Seer Sage, which was subsequently republished on Dulfy.net. I do not say this to assert that I am an expert, but rather to explain why I have a focused interest in this particular class and spec to the exclusion of others.

During that time, I have been keenly following the theorycrafting work of the likes of KeyboardNinja, Dipstick, Bant, Vicodin, Schwarzschilda, and others. With the exit of Bant from the scene and the advent of a new tier of gear (252 and 258), I decided at that time to essentially replicate a large portion of Bant's work for 258 gear while keeping the scope of it small and manageable by focusing exclusively on Seer Sage.  As the game evolved and newer, higher level caps and tiers of gear were introduced, I have continued to use this methodology to evaluate the new gear.

Of course, everything here applies equally to the Corruption Sorcerer, but from this point on I will only use the Sage terminology for simplicity.
Assumptions:

1. The most fundamental way to break down two gear sets for comparison is to calculate an average HPS (Healing Per Second) for each set, and the one with the higher value is considered better.
2. The effect of Crit can be quantified by averaging out the "Crit Multiplier" damage with the "Crit Rate", effectively assuming that the actual "Crit Rate" is EXACTLY the stated Crit chance.
3. The effect of Alacrity can be quantified by calculating its effect on the cast times of each ability, and using that adjusted (shorter) time as the base denominator of the Healing-Per-Second ratio.
4. Most Sage healing abilities are Force-negative, in that they use more Force than the Sage regenerates during the cast-time and could not--even if ability cooldowns allowed it--be used repeatedly, indefinitely. As such, Seer Sage gameplay includes the need to actively use Vindicate to replenish the lost Force so that healing can be maintained at a high output level over a long period of time. This means that, for a fair comparison, individual abilities would have to have their HPS calculations "penalized" for being Force-negative (since you can't use them indefinitely without devoting additional time to Vindicate), and the "penalty" would have to be proportional to the magnitude of the Force-negativity.
   
   This phenomenon is, in a practical sense, unique to Seer Sage and the fundamental reason for this alternate calculation method. The closest analog to this in other specs is the need for Force-positive/ammo-positive "filler" abilities in order to maintain a Force-neutral/ammo-neutral rotation. However, these filler abilities all have healing/damage effects of their own, where Vindicate does NOTHING but recover Force so it cannot have an HPS score of its own.
   
   With that said, I believe the technique of normalizing HPS/DPS scores to make each ability Force-neutral or Ammo-neutral could be applied to other classes and specs, and I will leave that up to the rest of the community at this time.
   
   
5. The goal of the "penalty" will be to normalize the ability so that its HPS value represents a Force-neutral use of it. In this way, all abilities can be fairly compared to each other (and represented as a meta-ability than CAN be used indefinitely).
6. The way to normalize all abilities to Force-neutral status is to inflate their cast times to include the time required to use Vindicate to recover the Force lost in casting the original ability. This extra time penalty will be some fraction of a GCD.
7. In the event that an ability is actually Force-positive, the "penalty" will work in the opposite direction, reducing its practical cast time and inflating its HPS value accordingly.
8. Some abilities are exceptions, such as Force Mend (which, being off-GCD, has a practical cast time of ZERO) and must be treated separately.
9. It is possible (and even likely, in light of abilities which never crit or which auto-crit) that the optimal stat setup and gear itemization for one ability will not be the same for all abilities. To address this disparity, a "weighted average" can be used based on the relative actual use of each ability in real combats (using Combat Logs as a data source) to determine a "best overall" stat setup and gear itemization.
10. In order to calculate the best possible result, we will assume 100% perfect play (e.g. maximal APM and perfect use of Respendence stacks with Vindicate).

Methodology:

This is the process by which I determine the HPS of a given ability.

Step 1: Recalculate the base minimum and maximum amount of healing done by a given ability according to the gear and stats presented.

Doing this requires insight into both the formulas that the game uses to calculate damage and healing, and the individual constant values used for each ability. My source for this information is a combination of data mining information from Jedipedia.net, TORCommunity, and reviewing the work already done by Bant.

Note that these results can and should be sanity-checked against the the values presented in-game by the Character sheet and the ability tooltips. If those values do not match, it is pointless to proceed. Also, if all you want to do is check the methodology, you can skip this step and simply use the values presented in-game for a given gear set.

Step 2: Average the low and high value.
(If there is only one value given, then that is the average.)
Avg = (Min + Max)/2

Step 3: Adjust the average for Critical Rating and Critical Multiplier.
Crit_Adjusted = Avg + (Avg * {Crit Multiplier%} * {Crit Chance%})
The {Crit Chance%} and {Crit Multiplier%} (formerly called "Surge") must match what is shown in-game as explained in Step 1.
Note that {Crit Chance%} already includes such adjustments as the Smuggler class buff and the 3% bonus inherent in the Seer spec.
(See the sidebar later in this post about this formula and how it accounts for the "Super-Crit" effect.)

Step 4: Determine the actual Cast Time of the ability.
This takes the character's Alacrity into consideration, including the determination of whether the ability is instant-cast or not.
CastTime = BaseCastTime / (1.0 + {Alacrity%})
The BaseCastTime here is the cast time reported in-game (and found in the data mining info) for the ability when the character has ZERO Alacrity. If the ability is instant-cast, then BaseCastTime is 1.5 seconds (the standard, unmodified GCD period) and the resulting CastTime must be rounded up to the nearest tenth of a second (see Step 7).
Like Step 1, if you just want to check the methodology, you can simply use the values presented in-game.

Step 5: Calulate the amount of Force regenerated naturally during the cast time.
This requires knowing the character's Force Regeneration rate and the actual cast time of the ability.
RegenRate = 8.0 * (1.0 + {Alacrity%})
ForceRegen = RegenRate * CastTime

Step 6: Calculate the net Force loss from using the ability.
Assuming the ability is Force-negative, this is the magnitude of it.
ForceLoss = {ForceCost} - ForceRegen
The {ForceCost} here is the value reported in-game (and found in the data mining info) for the ability.

Step 7: Determine the Cast Time of Vindicate.
Although this is an instant-cast ability and uses the GCD as its cast time, the GCD is affected by Alacrity so we must take that into consideration, including the unique rounding factor that only applies to the GCD.
Time = 1.5 / (1.0 + {Alacrity%})
GCD = Time, rounded UP to next highest tenth of a second

Step 8: Calculate the ratio of Force Loss to Force recovered by a single Vindicate.
For this calculation, we use a value of 45 for Vindicate, which assumes proper use of Vindicate only with stacks of Resplendence (adding 5 additional Force to the base 40 points). You can adjust accordingly if you do not want to make that assumption.
Fraction = ForceLoss / 45
Note that, the value used for Vindicate could previously be adjusted in the presence of the Force-Mystic set bonus, but this is no longer available in game version 7.x.

Step 9: Calculate time consumed by a partial Vindicate which recovers the exact Force lost during the cast.
To put it another way, apply the ratio of Force Lost vs.Total Force Recovered to the time spent casting Vindicate (treating Vindicate as if it were a channeled ability that could be clipped at precise moments to recover exactly the desired amount of Force).
VTime = Fraction * GCD

Step 10: Adjust the Cast Time of the ability by adding in the partial Vindicate from Step 9.
This results in a new Adjusted cast time that includes just enough Vindicate time to cancel out Force-negativity.
CastTime_Adjusted = CastTime + VTime

Step 11: Calculate average HPS, adjusted for Force-neutrality, using the above results.
HPS = Crit_Adjusted / CastTime_Adjusted

This becomes the weighted Healing Per Second score for the given ability that is used to evaluate changes to the gear loadout and resulting stats.

A Sidebar on Step 3:

The formula is Step 3 is interesting because, while it intuitively looks too simple to be taking all of the Critical effects (especially the "Super-Crit" effect which was introduced in game version 4.0) into account, it actually does do this because the more complex version of the formula has factors that cancel each other out.

Here's the breakdown:
We start with the Base Heal (or Damage):
Base
If there is a critical heal, the Base is multiplied by the Critical Multiplier percentage (formerly called "Surge") and added to that base.
Base = Base + (Base * Surge%)
The chance of a critical heal happening is the Critical Chance percentage. To average out the crits and the non-crits, we can simply multiply the Critical Chance by the additional damage.
Base = Base + (Base * Surge% * Crit%)
BUT . . . this is incorrect in the case where the Crit Chance is over 100%. So we account for that by assuming that anything above 100% is an automatic crit and we should treat it as 100% instead.  This would be the final correct formula for game versions prior to 4.0.
Base = Base + (Base * Surge% * MIN(Crit%,100%))
Version 4.0 introduced the "Super-Crit" effect, where excess Crit Chance over 100% is applied to the Critical Damage as an additional multiplier. (So, for instance, if your Crit Chance is 130%, your Crit damage is additionally increased by 30% after all the other factors are calculated, so you can easily get there by multiplying by 130%.)
To account for this effect, we add:
Base = Base + (Base * Surge% * MIN(Crit%,100%) * Crit%)
BUT . . . now this is incorrect in the case where the Crit Chance is NOT over 100%. So we account for that by assuming that anything below 100% is not a Super-Crit and we should not change the result. We can neatly do that by treating it as 100% instead--which is the same as multiplying by 1.0.
Base = Base + (Base * Surge% * MIN(Crit%,100%) * MAX(100%,Crit%))
Now take a closer look at the last two factors:
MIN(Crit%,100%) * MAX(100%,Crit%)
If Crit% < 100%:
MIN(Crit%,100%) * MAX(100%,Crit%) = Crit% * 100% = Crit%
If Crit% > 100%:
MIN(Crit%,100%) * MAX(100%,Crit%) = 100% * Crit% = Crit%
If Crit% = 100%:
MIN(Crit%,100%) * MAX(100%,Crit%) = 100% * 100% = 100% = Crit%
In all three possible scenarios, those two factors, multiplied together, simplify into just the Crit Chance percentage.
So by substitution . . .
Base = Base + (Base * Surge% * MIN(Crit%,100%) * MAX(100%,Crit%))
becomes
Base = Base + (Base * Surge% * Crit%)
...which is the formula presented in Step 3. Q.E.D.

In my opinion, it is possible that the BioWare Combat Team, when developing game version 4.0, chose to use a simpler formula for calculating critical results, and in doing so inadvertently gave birth to the "Super-Crit" effect, and simply decided to keep it this way.  Whether inadvertent or not, this had the additional (and possibly desired) effect of making Crit Rating relevant again in version 4.0, since throughout versions 2.x and 3.x the Theorycrafters of the time were instead recommending minimizing Crit Rating while maximizing Power and "Main Stat" (now Mastery).

A Very Interesting Result:

Using this methodology, I calculated the best gear sets for each of 12 heals, and the results were remarkably consistent. The Seer Sage spec does not have any auto-crit abilities nor any abilities with special bonuses to Crit other than Healing Trance and Deliverance when used with the Conveyance proc. The only outlier is the amount of HP absorbed by Force Armor, which is an ability that does not crit, so the best gear set for it (and ONLY it) features minimum Crit Rating and maximal Mastery and Power.

Every other ability followed the exact same trends:

• More Crit was always of more benefit to average HPS than more Mastery.
• This held true whether or not we adjust effective cast times to penalize for Force-negativity.
• The tipping point where Mastery DID become more beneficial than Crit is when the actual Crit Chance percentage reached 50% or higher.  At that point, holding the Crit Chance at exactly 50% and increasing Power and/or Mastery improved HPS more than increasing Crit so that it exceeds 50%.
• Alacrity is definitely beneficial. In all cases, overall HPS improved at the points where the GCD dropped by a tenth of a second.
• However, after a certain Tier of Alacrity is reached (1857+ for Tier-2 at Level 70 and 2054+ for Tier-1 at Level 80), more Crit was strictly better.  This was due to the strong shifting of the Diminishing Returns effect onto Alacrity and off of Crit, and more generally because at these levels the amount of remaining Crit points available falls well below recommended levels.  This held true for subsequent, higher gear tiers.
• If you are NOT applying the Force-negativity penalty (skipping steps 4-9), then the abilities with cast-bars and channels (Deliverance, Benevolence, Salvation, Healing Trance) would show a slight improvement by sacrificing Crit for more Alacrity. The instant-cast abilities (as you would expect, since they would be unaffected by the speed increase) showed a loss by doing the same. The loss on the instants was more significant than the gain on the channels.

Because of this observation, it appears that Assumption #9 above is actually not true--or rather mostly not true--even if it is simply due to coincidence. In fact, the optimal configuration for 11/12 abilities is the same, so no weighted average of ability usage is actually required to form a useful conclusion.

Evaluating Relics

The question of which relics to choose is the next obvious question, and the simplest way to evaluate them is to project what their effects on the overall stats would be, tempered by the possible uptime, and compare the effects on the HPS of the various abilities.

For simplicity, we will assume that all relics are used in a "best-case-scenario" fashion, which means that automatic-activation relics will activate as often as possible, and that click-to-activate relics will be clicked as often as possible.  That leads to this formula:

Improvement% = (BoostedHPS - BaseHPS) * (Uptime%)

...where BaseHPS is the normal HPS calculation for a given ability and BoostedHPS is the same calculation done while including the additional stats of the relic while activated.

Here are the relevant relics, in order, using Wandering Mend as an example ability:

Note that the amount of boost from each of these relics is relatively small (just over 2% at best) and the difference between them is mostly negligible, so the practical difference between using any given pair versus any other given pair would not even be noticeable.

Close analysis of the effects of each shows some practical reasons for the difference.  The issue at hand is approaching and/or exceeding the 50% Crit Chance threshold.

The reason for Serendipitous Assault's superior results is that it improves Power rather than Mastery, which has a 3% better improvement to the Bonus Healing score, without affecting Crit.

Focused Retribution, on the other hand, trades off that 3% benefit for a slight improvement in Crit Chance, but that improvement does not exceed the 3% benefit due to diminishing returns on a high Crit Rating.

Primeval Fatesealer does quite well in improving HPS (and uniquely by reducing the denominator rather than increasing the numerator)--more than FR or SA in fact--because it applies enough extra Alacrity to push the player's GCD from 1.4-seconds to 1.3-seconds, benefitting all abilities rather than only channeled/casted ones.  However, its comparatively lower total uptime reduces the HPS benefit, causing it to land just under FR.

Devastating Vengeance suffers most because it adds a large amount of Crit Rating directly, large enough to exceed the 50% threshold where more Power or Mastery is strictly better.

Evaluating Set Bonuses (Implants)

The question of which set bonuses to choose is beyond the scope of this document since this methodology is strictly concerned with stats, and set bonuses normally modify existing abilities and/or indirectly create new ones.

As such, the choice of set bonuses (at Level 80 this means the choice of Implants), is simply left to the preference of the player, but the stats attached to those chosen implants are then to be considered immutable.

For reference, I have chosen Rejuvenation and Unmatched Haste which both carry Crit Rating as their tertiary stat.

Best-in-Slot Gear Totals

Based on these results, the BiS configuration for Seer Sage is:

Using 258-rated gear and 240-rated augments (Game Version 5 / Level 70)
Critical: 5E + 8A + 2C (2287)
Alacrity: 5E + 6A (1859) [Note: The Alacrity total for a 1.3-sec GCD is 1857+]
Accuracy: 0
Stim: Red - Mastery/Power
Relics: Serendipitous Assault and Focused Retribution

Using 344-rated gear, 340-rated implants, and gold 300-rated augments (V7 / L80)
Critical: 5E + 2I + 12A + 2C (6070)
Alacrity: 3E + 2A (2180) [Note: The Alacrity total for a 1.4-sec GCD is 2054+]
Accuracy: 0
Stim: Red - Mastery/Power
Implants: Rejuvenation (Crit) and Unmatched Haste (Crit) [Note: This is the "2I" above]
Relics: Serendipitous Assault and Focused Retribution

Purely a coincidence, but an easy shortcut to 5 Crit and 3 Alacrity pieces is to simply use nothing but the Force-Healer items from head-to-toe, including lightsaber and focus (of course, the relics and Bracers/Belt are irrelevant) and an Adept (Crit) earpiece.

The healing abilities compared were:

1. Healing Trance
2. Rejuvenate (Initial heal)
3. Rejuvenate (Heal-over-Time follow-up)
4. Rejuvenate (Renewal skill-tree effect)
5. Deliverance
6. Benevolence
7. Salvation
8. Wandering Mend
9. Force Mend (Ignoring zero-length cast-time)
10. Restoration (The associated heal effect)
11. Force Armor
12. Soothing Protection (Side-effect heal of Force Armor)

Originally, this list also included the Psychic Suffusion utility effect on Force Wave, but that effect no longer exists in game version 7.x.