I would like to know the critical damage multiplier of some class in order to develop better builds (up untill now the only thing I cared about was that for my priest I had something around x1.5 multiplier for crits).

In particular, I would like to know the critical multipliers for warlocks and mages. I couldn't find these info written anywhere, but I know they are known (they are needed to evaluate correctly the dps). Anyone that can help?
Also, if I'm not wrong, arcane, fire and ice have differents crit multipliers, is the damage multiplier based on the type of damage (rather than on class)?

Thanks for any help.