200% would mean you heal as much as you would have taken damage. Not that you got immunity.
Before you said 200% = 0% damage, I was somewhat thinking you might be mistaking percentages with denominators (dmg * 1/(1+res)
is a common formula, but notably is not using percentage for the res stat) or asymptotes (such as dmg ^ (1/res)
, which again is not a percentage).
But for a formula that has 100% damage at 0 res, 50% or 25% at 100 res (which you mentioned earlier), but 0% damage at 200 res, you would need something like 100 - res / 2
(which would make res half-percentages instead of percentages) or 0.000025*res^2−0.01*res+1 = (1-res/2)^2
(not percentage related at all) to achieve that 75% reduction at 100.
No matter how I crunch the numbers to invent formulas, I can't think of any way to make a percentage-based resistance stat produce anything but a 100% reduction at 100%. Mainly cause that is pretty much per definition what a 100% resistance/reduction stat means.
If you had been thinking 200% meant twice as much damage, instead of 0% damage, then at least I could have assumed you mistook resistance for weakness/susceptibility (so immunity would be at 0% instead, and higher = more damage taken). But you showed clearly that isn ot what you were thinking. And so I am lost at trying to guess your thought-process that gets a 100% reistance to anything but a 100% resistance.