On the mechanics of ACC/DEF

[JusticeBowler]

My brain says, if I have a defense buff of 10% and a tohitdebuff on the baddies of 10% that puts my total defense at 70% (given you start at 50% chance to hit). That seems like a a 40% reduction in damage. if I add to that 10% res then I'm reducing damage 46% since I'm reducing 10% of the remaining 60% I'm still taking.

 

But I'm not sure that's how tohitdebuff works. Obviously with a higher base ACC for LTs and bosses (or +x minions)... the effect is less useful than that, but I thought I'd ask the question for folks who might have worked this out.

 

I remember somewhere there was a right up as to exactly when each aspect of damage reduction over all was applied to the equation, but I don't remember where.

 

 

[Adeon Hawkwood]

You're right but you're coming at it from the wrong direction. To Hit Debuffs do stack with Defense but the calculation is in the opposite direction. Most NPCs have a base To Hit chance of 50% and your Defense and To Hit debuffs are subtracted from that (with a minimum value of 5%). So 10% defense and 10% to hit debuff means that the enemies will hit 30% of the time which is indeed a 40% reduction in damage.

 

A few other things. First Lts and Bosses do have a higher accuracy but since accuracy is applied after defense and to hit debuffs having more of them wn't help, so the defense softcap is still 45% (with to hit debuffs contributing to that).

 

Secondly debuffs have reduced effectiveness against enemies who are higher level than you so you need to be a bit careful about relying on them when fighting at higher difficulties. They are still effective, but they won't mitigate as much damage as they do against +0s (unlike defense which is equally effective up to +4s).

[JusticeBowler]

Also there's the question of -RCHG which seems to function mathematically like RES, but it much more effective because it pulls off the attempts to hit rather than only reducing the damage of the remaining hits.

 

If a power has a -10% tohitdebuff or a -10% defense (assuming +0 minion) and so we only get hit 30% rather than 50% of the time. So, as I mentioned -10% RES would only be a -6% actual reduction (since it is resisting a smaller amount), but a -10% RCHG would "come off the top" as it were reducing the total damage more effectively regardless of how close you get to the DEF soft cap.

 

I'm still curious about the actual underlying equations for how the system computes damage. Somewhere everytime a mob tries to hit me (or me hit him) there's a series of basic calculations with all the variables in their place (including boss bonuses or mob +4 bonuses, etc).

[_NOPE_]

You also have to factor in controls, both soft and hard, which affects the ability of a mob to fight back. I've always said that knockback is 100% DEF for 4-6 seconds at a time.

[srmalloy]

I've always said that knockback is 100% DEF for 4-6 seconds at a time.

 

Although it may not kick in immediately; you'll get your interval of complete defense, but if they've already started their attack when you hit them with the knockback/down, the attack will still go off if it's not a Snipe or other interruptible power. You'll just get it after they shoot.

[JusticeBowler]

You also have to factor in controls, both soft and hard, which affects the ability of a mob to fight back. I've always said that knockback is 100% DEF for 4-6 seconds at a time.

 

I love knockback as much as the next guy (assuming the next guy isn't you), but there's a caveat even to this. If a knockback (or hold) effect transpires while the mob's powers are recharging then there is zero damage mitigation. To the extent that the attack chain of a given mob is even momentarily delayed (they had a ready attack and have to wait a couple of seconds to execute it) then we have damage mitigation.

 

In practice, I'd put the mitigation far lower than one would find desirable. This is especially noticeable when one is soloing a controller and fighting a Boss or LT and one's health is already impaired. The hold often feels like it isn't helping and my argument might be that it wasn't all that much. If all you do is give the Boss time to wind up their really big attack and wallop you, the experience (regardless of the math) will be less than optimal. :)

[ed_anger]

You also have to factor in controls, both soft and hard, which affects the ability of a mob to fight back. I've always said that knockback is 100% DEF for 4-6 seconds at a time.

 

Knockback may be useful for solo toons, but it’s one of the most irritating powers in groups. If you’re trying to AOE or melee mobs and someone keeps scattering them then knockback is increasing your time to kill.

[_NOPE_]

If that's happening, then the person needs to LEARN2KB!!!

[GnomeDePlume]

Bounded[ NetToHit = (InherentAttackAccuracy) * (1 + AccuracyEnhancement) * Bounded[ BaseToHit + ToHitBuffs - ToHitDebuffs - (Defense - DefenseDebuffs) ] ]

 

Where Bounded[x] is the result of setting x to be 5% if x is lower than 5%, and 95% if x is higher than 95%. Notice that bounds checking is done twice: first after tohit and defense are combined (cf: the simplified tohit formula) and then again after accuracy buffs and debuffs are factored in.

 

(In excel terminology, Bounded(x) is MIN( MAX(x,0.05), 0.95) )

 

 

From:

https://web.archive.org/web/20120903224303/http://boards.cityofheroes.com/showthread.php?t=121258

 

[jack_nomind]

the above formula is my chief argument for some all-in defense sets having at least a little elusivity in PvE.

 

Softcapped defense doesn't mitigate 90% of damage in a lot of cases where it matters because the relevant enemies have 1.69x or more Accuracy.  This is particularly bad when the actual softcap isn't reached for some reason, whether it's a tohit buff or defense debuff.  0.050 x 1.7 = ~0.085, which is bad enough; it cuts 90% mitigation down to 83% and there's nothing anyone can do about it.  But a little higher, say 0.075 base tohit, and you're down from 85% 'expected' absolute mitigation to <70%.  That can be mitigated with a purple, but that's a little like saying damage can be mitigated with greens.

[plainguy]

The links in my Signature were very helpful to me back in the day.