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Is Expertise-DR additive or multiplicative with base DR?

STAR WARS: The Old Republic > English > PvP
Is Expertise-DR additive or multiplicative with base DR?

Khalhazar's Avatar

01.31.2013 , 06:13 PM | #1
The formula thread, etc. is unclear about this, so I wonder if anyone here knows the answer. If i receive X base damage from another player, is the result:

(a) X*(1-(base-DR + playerDR_from_expertise))
(b) X*(1-baseDR)*(1-playerDR_from_expertise)

Put another way, is my mitigation % of player energy/kinetic damage:

DR: 52.68%
Expertise: 19.96%

(a) 52.68 + 19.96 ~= 71.64%
(b) 52.68 + (1-52.68)*0.1996 ~= 61.65%

I know this is a rather obscure question, and very few PvP tanks will actually care, but it is important to me as I strive to optimize. Thanks for your time.

(Edit: when I say DR I mean damage-reduction. Sorry.)
Semah Valerian <Some Sith and a Spy> | Juggernaut | Begeren Colony

DarthBloodloss's Avatar

01.31.2013 , 06:23 PM | #2
I would like to guess multiplicative. I realize this helps you 0%, sorry. I have nothing to back this up.

I just wanna see if I'm right!

(edit: changed my answer when I looked at the formulas)
Bloodloss Mercenary

tekhiun's Avatar

01.31.2013 , 06:24 PM | #3
If any competent dev would make it multiplicative as the dmg buff is . However we are talking about bioware so its probably additive.
Star Wars: Attack of the Cartel.

funkiestj's Avatar

01.31.2013 , 06:55 PM | #4
damage buff & damage reduction are multiplicative. For any given expertise, damage buff and damage reduction are inverses (i.e. cancel one another out).

There is a BW dev interview that says this. For excellent discussions of SWTOR formulas see

Quote: Originally Posted by James Ohlen
Expertise was designed so that the damage bonus and the damage reduction effectively cancel out for two players with the same amount of expertise, and this should remain true in patch 1.2 as well. However, the way the damage bonus and damage reduction are applied changed in patch 1.2, and this resulted in the two values no longer being the same on the character

Prior to patch 1.2, these values were additive, like so: Damage * (1 + Attacker_Exp Target_Exp)

This system was simple and worked for players with similar amounts of expertise but breaks down for large differences in expertise values. For example, consider player A with 50% expertise fighting player B with 0% Expertise. When A attacks B, he does 150% damage, and when B attacks A, he does 50% damage. This means Player A gets a 50% damage boost as intended, but that 50% DR boost means he gained 100% survivability (player B is doing 50% damage, so he now must deal twice as much damage to kill player A).

In patch 1.2, this formula was changed so that these values are now multiplicative, like so: Damage * (1 + Attacker_Exp) / (1 + Target_Exp)

So using our 50% expertise example again: When A attacks B, he still does 150% damage, but now when B attacks A, he does 1 / (1 + 0.5) ~= 67% damage. On player A's character sheet, this shows up as 50.00% damage boost and 33.33% damage reduction, which are inverses of each other (player A deals 50% more damage to player B, and player B must deal 50% more damage to order to kill player A). Note that they'll still cancel out for two people with the same Expertise value, just as they did pre-patch 1.2.

Healing is on a completely separate balance axis, where we use expertise vs. trauma to get the healing rate we want in PvP

Mr. Hat says "BW support is the best"!
I am a bad player, so what?

DarthBloodloss's Avatar

01.31.2013 , 07:07 PM | #5
So for an attacker with +10% damage boost.....and a defender with 20% mitigation. There is still 10% mitigation does that apply to Armor Rating Damage Reduction? Does it add the straight 10% (to the armor's damage reduction of 30%, making the total 40%) or does it mitigate 10% and then mitigate 30%?

In this example, the end result is nearly the same...but a straight 40% mitigation is slightly better.
Bloodloss Mercenary