Is there anybody there who has checked the base cold resistance of hell monsters ?

"High cold res" is the vast majority of them, that is to say any monster with positive cold res (where having more than a final -100% worth it).

Of course you should max cold mastery !

And as a sidenote, hybrid sorceress is mainly :
max frozen orb (synergy and cold mastery)
+ some static, possibly thunder storm
+ firewall

You will have plenty skill points to allocate...

Non cold immuned are easily killed (help from static in some situations).
Cold immuned are reduced to very low hp with Static, and finished off with firewall/TS.

If you want to skip cold immuned, then use Blizzard instead of frozen orb.
And then, you won't have any skill point to lose in fire or light tree => pure cold sorceress.

This post was edited by feanur on Oct 17 2018 03:42pm