Armour reduces damage from every incoming melee and ranged weapon attack, even if it is not physical damage. It does not work on physical attacks that are not weapon based, such as. It does not work on damage from sources that are not weapon-based, such as spells, mental attacks, or breath weapons.
There are three values which work together to determine the final outcome:
- Armour penetration (APR)
- Armour hardiness
The attacker's APR is subtracted from the target's armour value. Armour hardiness is the maximum percent of each incoming attack that can be absorbed. The primary method of increasing armor hardiness is via the Armour Training talent, however some artifact armors, cloaks, and shields also affect the value.
The final resulting damage reduction is:
min( (Armour - APR), (Hardiness * damage) )
At 0% hardiness, your armour absorbs no damage at all. At 100% hardiness, your armour absorbs any damage up to the actual armour value. At 50% hardiness, up to 1/2 the damage will be absorbed, but no more than your total armour value.
We assume a defender with 30 armor and 50% armor hardiness, and an attacker with 5 APR.
- You are hit by an attack dealing 100 damage. (Armour - APR) is 30 - 5 = 25, and (Hardiness * damage) is 0.5 * 100 = 50. Since 25 is smaller, your armour absorbs 25 damage, and you take 100 - 25 = 75 damage.
- You are hit by an attack dealing 10 damage. (Armour - APR) is 30 - 5 = 25, and (Hardiness * damage) is 0.5 * 10 = 5. Since 5 is smaller, your armour absorbs 5 damage, and you take 10 - 5 = 5 damage.
Armour is applied before all kinds of critical damage increase, talent multipliers and weapon damage range multiplier, thus making even small amounts have greater effects. For Example, with 50 armor and 100% armor hardiness, if you are hit by an attack that does 100 damage, but has a 300% talent multiplier, it will do (100 - 50) * 3 = 150 damage. Another consequence of this system is that multiple small hits are not affected by armor moreso than a stronger hit, provided their % damage sums to the same amount: 4 hits at 100% damage are affected by armor the same as 1 hit at 400% damage.
Reducing an enemy to below 0 armour does not cause bonus damage.