1) He has ~6 sec of immune and you don't need to kill mobs near chest in full MF equip. For example in group chest farming act 3 i take my loot from 1st try in 2-4 sec. While wizards/DHs has great problems when elites are near the chest.
2) I am soloing inferno act 2-3 goblins in 300 MF from gear (w/o NV). In burst zombie-bears spec with 9k DPS it dies without any problems.
For killing elites IMO the best classes are:
U have to gear up melee in expencive def. stats to make it farmer.