A Mage/Necromancer is what I run for doom gauntlet and he works very well. Your going to want to save up for a 120 magery PS as you will be casting many EE's, EV's and Earthquake's, while you could go at GM your going to find the fizzling will get to you so you will want to get to 120. I find an LRC suit is a must, try to leave hands free for a scrappers spellbook which seems best for rooms 2,5 and I find the DF. An Undead spellbook works well for rooms 1 and 4, and a Demon spellbook for room 3, can also use against DF and room 5 though I find I do better with scrappers there.
My template
120 Magery
120 EI
120 Med
120 Necro
120 SS
the rest I have in MR but that is because I also do alot of champ spawns in Fel, if your not going to Fel you could easily drop and add spellweave for a WoD (word of death) great finish spell. Probably dont need 120 Necro either could get away with GM easily enough. I find I spend alot of time in wraith form to get mana back when I unload attack spells.
I usually use my mage/tamer for peerless runs so while I figure my necro/mage would do well I havent actually tried him, I like to dust off my other chars once in awhile and let them out to play
