Iron wolves actually don't really do much damage. An act 5 with a good sword would be good for physical damage, and an act 2 with might and a good polearm would also be really good. In hell, the merc should be doing upwards of 1,000 physical damage. Dual-immunes would, of course, still be a problem :/ .

However, I think waiting a while before starting hell would also be good. I'd definitely wait until at least level 60, though it couldn't hurt to gain level 65 or so before starting.