I'll address this soon, as I've realized the seemingly endless pack of major wizards can be a pain to deal with. As [b][u]yahgohbee[/u][/b] said, just run back to the room where the very first major wizard you encountered in the strike appeared and take them out from the safety of the rocks and the rise that the stairs offer. When more enemies spawn during the runes, run back there - rinse and repeat.

Pop in and out of the room and kill all ads that aggro on you. Stay by the entrance and when Wizards cone, run up the stair way back to where you can see the Hellmouth, turn and snipe/rocket/unleash pain on them. Rinsw, repeat. Stay alive. Better to run and live than wipe and start all over again.