Well, if you want to do mephi and pindle make a blizzard sorc. Please specify what you are going to mf.
I have a level 81 MF sorc that is All fire. I 4-hit pindleskin in hell with fireball, and 1hit the minions around him. I take out mephisto in a quick 10-20 seconds while spamming meteor and casting fireball while my meteor down time is going away.