EE + Flamability + EW + Fire pen = too much??

Look at it this way.

You target a critter with a 100-damage Fire attack. That critter, for whatever reason, has the same 75% fire resistance any half-decent player build does. You have no resistance reduction or penetration, and so you deal 25 Fire damage with your 100 damage fire.

No let's assume that you trigger EE on the target, reducing its resistance to your damage from 75% to 25%. As such, you now deal 75 damage to the target, rather than 25 damage. You have, effectively, tripled your damage as compared to the 75-res basepoint.

Now. Via enhanced Flammability or whatever, let's assume you subtract another 50 resistance from the critter, putting it at -25 resistance. Your 100-damage fire attack now deals 125 damage. This is double your EE damage alone, which is big - but not as big as triple your damage, from the first EE effect. Double your damage < triple your damage.

That's what folks mean when they say that resistance reduction/penetration runs into diminishing returns. Eliminating positive resistance is vastly more important than increasing negative resistance values. Every point of resistance you take away is just a little bit less valuable than the point before it, and as such there comes a point where increasing your actual skill damage is a better use of limited build resources than taking an enemy at -250 Fire resistance and pushing it to -300 Fire resistance.

Most people treat that point as being the zero-resistance mark for easy convenience, or they treat it as "any significant penetration/reduction effect after the first two is overkill". EE yes. EE + Fire Pen, yes. EE + Flammability, yes. Fire Pen + Flammability, yes. EE + Fire Pen + Flammability + Elemental Weakness + Xoph's Blood + ...: too much. You have covered your penetration needs. Get extra damage or improve your defenses instead.

Thx everybody.

I edited a previous post and corrected my math.

I came to the conclusion that I will nevertheless keep the fire pen because it gives me an effective 42% damage boost vs 40% fire resistance bosses that I hit with EE, EW and FP.