I am sorry but most of you guys (if not all) are all wrong. the perfect combo against hell meph is:
Frozen Orb(10pts.), Cold Mastery(maxed), Thunder Storm(maxed), Lightning Mastery(maxed), Static Field(1pts.).
Best Def is:
Mana Shield(1pts.), Shiver Armor(1pts.), Warmth(4pts.) A Rhymed Luna Shield(runeword), Lightning/Ice Resist, Life/Mana and Armor Def Charms.
The reason why you only put in 1pts. to those other skills is cause you need Occulus, Harleyquinn Shako and tals armor/skullders ire and anything that will add skill points to all. they will beef them up to eight points at least. If you get two occyrings as well they can be bumped up to 14pts. each and 18pts. to your warmths.
My char has this sort of set up for hell mephbotting and the death rate of meph vs. you is 150/0 on average. only on odd days does he ever kill me. Just remember to only put your char points like this:
str:100(nothing more over 100)
dex: (
no points added)
vit:maxed (do this last)
enr:100-150 (plus charms and armor bonuses)
I swear this set up kicks butt.