For those who do not know, there are 2 resist mechanics for spells. Resist based resists and level based resists. It seems in most calculations, people assume that those are additive. For example, if you have 10% mitigation from resists and 10% mitigation from level difference, most assume that your total mitigation is 20%. But if the resists were multiplicative, it would be 19%, since the second resist would be 10% of 90% or 9%.

This occurred to me when following the discussion about innate resists and how binary spells can counter innate resists with to hit since for those spells both resist rolls are rolled into one. It seems that the most commonly held theory is that spell penetration is applied first, then negative resists are set to 0, then the 8 resist per level difference is applied and then to hit is applied. That explains why –resist cannot overcome the innate resist and why to hit can counter it for binary spells. But wouldn’t that also imply that resists are applied multiplicatively since the level based resist is only rolled on the non-resisted damage?

Could somebody please explain this to me? I don't follow.

http://forums.worldofwarcraft.com/th...10271182&sid=1