How to best build up dual-tree sorceress? I am thinking of starting to build a Fire/Cold sorceress, for PvM single player. This will be my first serious Sorceress, after some builds just to try out things and see what I like. I have a 2 questions: 1) in developing skills, would you recommend first to build up one tree (Cold) before starting on the other (Fire)? Or is it better to build them up at the same speed? The first option will probably mean I'll go through Normal / NM quicker, but I will have problems with immunities. 2) How common are dual-immunes in NM and Hell?