If we're talking about having the best gear up to beating that boss, I would say Yagluth, meteor spam and any goblins that spawn make it quite difficult, you also need fire resistance or get vaporized immediately by meteors or if you run out of stamina right when he does his beam attack. Even with max armor and weapons you have to be careful.

If we're talking killing the boss in suboptimal gear then Bonemass. He's a DPS check.