how to calculate damage against mobs?

Hi!
I'm very interested in how to calculate damage in this game since penetration stat came out.

I was wondering if this would be the best channel before i 1.) reverse client 2.) host my own server.
I preferably don't want to start reversing the AC just to see the the formula so maybe someone of you already would know.

I tried collecting numbers in excel too, but the even simple crit damage increase seems to behave very weird (amp didn't really seem to affect crit damage too much etc).