SWTOR Tank School: Stats

Chapter 4: Tank Stats

How do Defense, Shield, and Absorb actually work?

SWTOR has quite a bit of depth, and this is one area where that complexity shows through. To help explain how the system works, we'll start with a simplified version of how damage mitigation works and then expand into the finer details after we've established the fundamentals.

So you're a tank and some enemy attacks you. This sets off a chain of calculations to determine how much damage you actually take. Here's how it goes:

1) First, there is a check against the enemy's Accuracy. Normally, an enemy will have a standard 100% Accuracy, so it's a non-issue. BUT, there are special abilities (such as Sundering Strike, which applies a 20% Accuracy reduction) that can reduce an enemy's Accuracy below 100%.

If the enemy's attack MISSES you, then you take ZERO damage.

2) Then there is a check to see if you RESIST the attack. You have about a 5% chance of this (so do DPS and healer characters) and things like special abilities from your skill tree can increase that, along with some other factors such as being a higher (or lower) level than the enemy.

If you do successfully RESIST the attack, you take ZERO damage.

3) Next, there is a check to see if you are buffed by a special ability to avoid damage, such as Saber Reflect or Resilience.

If you have recently activated such an ability, you take ZERO damage.

4) Finally, there is a check against your DEFENSE rating. If you have, for example, a 20% Defense chance, then that means you have a base 20% chance to successfully defend against the attack. Note that if an enemy has improved Accuracy, then every percent of Accuracy above 100% is deducted from your Defense percentage.

If you do successfully DEFEND the attack, you take ZERO damage.

At this point, you are going to take some damage, and we calculate how much.
For this discussion, let's assume that the attack would normally hit for 5000 HP of damage.

5) First, there is a check to see if you are protected by a damage-absorbing ability (such as Force Armor) or item (such as a Relic of Reactive Warding).

NOTE: This is NOT the same as your Offhand Shield item. For clarity, we will refer to this type of protection as a "Bubble"

This form of protection will absorb all damage taken, but no more than some fixed amount which depends on the ability or item itself. If the damage from the attack is less than the bubble's absorption, then you will take ZERO damage, and the absorption of the bubble is reduced by that amount. If the damage from the attack is more than the bubble's absorption (or remaining absorption from previous attacks) then the damage is reduced by the full (remaining) amount and the bubble is removed from you. So if the bubble is capable of absorbing a maximum of 1000 HP, the damage you take from the 5000 HP attack is reduced to 4000 HP.

If you are protected but a damage-absorbing bubble, the damage taken is reduced by the maximum amount that the bubble can absorb, possibly reducing the damage to ZERO.

Next, we reduce the amount of damage by your (appropriately-named) Damage Reduction percentage, which is mostly determined by your Armor Rating. There are additional factors that can increase it, such as skill tree abilities, set bonuses in your implants, or Tacticals. So if your overall Damage Reduction is 50%, the damage you take from the 4000 HP attack is reduced to 2000 HP.

The damage taken is reduced by your Damage Reduction percentage.

Next, we check against your SHIELD Rating percentage.

NOTE: This IS your Offhand Shield item.

The higher your SHIELD Chance, the more often you will take reduced damage due to your Shield activating. If your Shield activates, then the damage is reduced by your ABSORB Rating percentage. So if your Shield activates and you have an Absorb percentage of 40%, then the damage you take from the 2000 HP attack is reduced to 1200 HP.

If you successfully SHIELD the attack, the damage taken is reduced by your ABSORB percentage.

So this is how mitigation works. Using very realistic numbers, you can reduce the damage you take (in a best-case scenario) by over 75%, and have about a 40% chance of taking NO damage at all.

If you aggregate all of that together over the course of an entire operation, you will average out to actually taking approximately 20%-25% of the damage directed at you.

So lots and lots of Defense, so that I take NO damage as often as possible, is all I need, right?

Nope, for two reasons:

The first reason is that your Defense chance has an upper limit (35%), and you can never reach that percentage even if you had Defense points in the millions. Defense, like most SWTOR stats, is calculated on a curve that rises quickly at first, but slows as you add more and more points--and will NEVER reach that maximum value. This phenomenon is called Diminishing Returns.

For those of you with a bit of mathematics background, the stat curves are hyperbolic, starting at a constant 5% with a fixed asymptote at 30%. The actual equation for Defense percentage given your Defense Rating is:

DefensePercent = 5 + 30*(1 - (1 - (1/30))^((DefenseRating / YourLevel) / 1.2))

The 5 at the front is the base 5% you get even with zero Defense points.
The two appearances of 30 are the asymptote value at 30%.
The 1.2 at the end is the curvature value. A larger number is a more linear curve, and a slower rise in value.
The "YourLevel" is your character's level, but for levels 1-20, use the value 20. 
The equations for most other SWTOR stats (Crit, Surge, Shield, Absorb, Accuracy, etc.) are exactly the same, but with different constants for asymptote and curvature.

The second reason is more fundamental:

There are different "types" of damage, and some types ignore some forms of damage mitigation. So you have to have generous (and properly balanced) mitigation of all types (Armor, Defense, Shield+Absorb) so that you can deal with all types of damage.

So what are the damage types?

It's a bit confusing, due to the various names. There are 4 types of attacks and 4 types of damage that are combined in different ways, depending on the specific attack. They are:

Attack Types: Melee, Ranged, Force, Tech
Damage Types: Kinetic, Energy, Internal, Elemental

But in reality there are--essentially--only three types of damage because they are only combined in certain specific ways.

Here is a chart:

As you can see:
Melee and Ranged attacks are functionally the same--the difference is that Ranged attackers will shoot at you from a distance, while Melee attackers will run up close to you. M/R attacks can miss due to high a Defense chance.

Force and Tech attacks are functionally the same--the difference is that Force attacks are related to Jedi and Sith, while Tech attacks are grounded in real-world science. F/T attacks ignore your Defense, but can be partially blocked by your Shield.

Kinetic and Energy damage is functionally the same--the difference is that Kinetic damage comes from the physical impact of objects and/or ammunition, while Energy damage does not. For instance, a Sage's Project is F+K (throwing a rock), but Disturbance is F+E (throwing a ball of Force energy). K/E damage is basically the "normal" kind of damage.

Internal and Elemental damage (which most often takes the form of "bleed" damage) is functionally the same--the difference is that Internal damage comes from something applied directly to the target (such as poison), while Elemental damage comes from an external source (such as standing in fire). I/E damage is "special" damage that ignores Armor, Defense, and Shields. Internal damage is VERY dangerous, especially when it cannot be cleansed.

So if we review the sequence above, but take damage type into consideration, we have:

<list=1> <*> Check against the enemy's Accuracy, only if the damage is not Internal/Elemental.
If the enemy's attack MISSES you, then you take ZERO damage.

<*> Check to see if you RESIST the attack, only if it is Force/Tech damage.
If you do successfully RESIST the attack, you take ZERO damage.

<*> Check to see if you are buffed by a special ability to avoid damage, and if that ability is effective against the type of damage.
If you have recently activated such an ability, you take ZERO damage.

<*> Check against your DEFENSE rating, only if the attack is Melee/Ranged.
If you do successfully DEFEND the attack, you take ZERO damage.

<*> Check to see if you are protected by a damage-absorbing ability, no matter the attack or damage type.
If you are protected but a damage-absorbing bubble, the damage taken is reduced by the maximum amount that the bubble can absorb, possibly reducing the damage to ZERO.

<*> Reduce the amount of damage by your Damage Reduction percentage, only if the damage is not Internal/Elemental.

<*> Check against your SHIELD Rating percentage, only if the damage is not Internal/Elemental.
If you do successfully SHIELD the attack, the damage taken is reduced by your ABSORB percentage.


Okay, that's great. How does this help me?

This helps you in three ways:
<list=1> <*> As you get more experience with the game's enemies and learn what TYPE of attacks they use, you can better apply the RIGHT defensive "cooldown" ability at the right time.
<*> Looking at the descriptions of attacks, you can better judge how they will affect you. For extreme cases*, you might even change your gear a little bit.
<*> By understanding how the damage system works, you now can understand what relics to use, and why.

For example, suppose you are a Shadow tank, and a boss is about to use a powerful attack on you. Should you use <url=http://www.torhead.com/ability/Deflection>Deflection or <url=http://www.torhead.com/ability/Resilience>Resilience? Deflection increases your Defense chance dramatically, but if the attack is a Force/Tech attack, it won't help you at all. Resilience gives you a 100% chance to resist a Force/Tech attack, but if it's Melee/Ranged attack, then it won't do you any good.


How do I know what kind of attack and what kind of damage Ops bosses do?

This is where a combat log parser like Parsec comes in handy. After a boss fight, you can review a breakdown of damage taken, including how much damage was done by each attack, what type of damage each attack did, total damage taken for the fight, and Damage Taken Per Second (DtPS).


You mentioned extreme cases: Like what?

Let's suppose that you are about to fight a boss that you know in advance uses M/R attacks almost exclusively. Would you want more Shield & Absorb in your gear or would you want more Defense?

You'd want more Defense. So if you have the extra gear, you could switch out a few items that have mods with Absorb for the same items that have Defense mods. This would put you into a better position to mitigate more of that M/R damage.


What about relics? Which ones are Best-in-Slot?

This topic would otherwise belong in the previous chapter, where it is simply stated without any justification. Now that you've been introduced to damage types, you're in position to understand why.

Most damage inflicted on you in the game is through M/R attacks. This makes Defense very important to all types of tanks. Without question, the Relic of Fortunate Redoubt is the first tanking relic you should have. If you only have one, it should be this one.

Many tanks will use the Relic of Shield Amplification as their second relic. This is understandable, since it's readily available for purchase with Classic and Basic Commendations, and it's been in the game since launch. It is a good second relic, but it's not the best.

The Relic of Reactive Warding is the best second relic for 99.9% of the game. Why?

The Shield Amplification ("SA") relic works by giving you a boost to your Shield and Absorb rating when you successfully shield an attack. So right off the bat, there's a good chance that it won't proc for you if you have bad luck in getting your shield to activate (or if your Shield Percentage is low).

Also, the SA relic improves your Shield and Absorb Ratings, not Percentages. This means that the bonus added to your existing stats are subject to the Diminishing Returns described above. The better your gear, the less effective the SA relic is for you.

But the Reactive Warding ("RW") relic suffers from neither of these problems. It procs when you take damage . . . which means it will be "up" as often as it can be with minimal delays.

Since the RW relic provides an absorption bubble for a fixed amount of damage, it does not suffer from Diminishing Returns. As most, it fails to scale up with the amount of damage done by more powerful bosses.

But the RW relic does one more thing for you that SA doesn't: The RW relic will also absorb Internal/Elemental damage, while the SA relic does not. (Remember: I/E damage ignores your shield, so it wouldn't matter if both Shield and Absorb were boosted to 100%.) This is the factor that makes RW the clear winner over SA for 99.9% of the game.


You said "99.9% of the game" twice now. What about that last 0.1% of the game?

Yes, there are certain specific conditions where the SA relic is better than the RW--a

Suppose you have a boss that does A LOT of damage: so much that when you figure the actual boost to your Shield and Absorb percentages and multiply those fractions by the total amount of damage, the resulting additional damage shielded exceeds the fixed amount that is absorbed by the RW relic. In that specific situation--and ONLY that specific situation--the SA relic is superior.

The same people who've worked out the optimal gear mixes for each type of tank have also worked out the amount of damage required to create those conditions, and it is somewhere in excess of 2000 DtPS.

This situation does exist in the game, in exactly ONE place: Nefra, Who Bars The Way, the first boss in Dread Fortress HM. Nefra's relentless Twin Attack (which is over 93% of the damage done) exceeds 2200 DtPS, which makes it unique in all of SWTOR. It is also a Melee attack, which means that Nefra is also one of the "extreme cases" described above where increased Defense over Shield/Absorb works in your favor.