Just cleared it with no tank in a party consisting of destruction warlock, arcane mage, elemental shaman(myself), and a disc priest.

1st two bosses required some clutch saves via ice block, invisibility, earth elemental, and void walker taunt.

3rd and final boss... Well, we wiped the first two attempts and on the 3rd after the others died I just switched to ghost wolf and killed him with ice patches. If this ever ends up happening to you make sure to deal enough damage(no idea how much is required or if just getting the killingblow will work) otherwise you won't get credit thus no hc dungeon completion meaning to rdf rewards nor were we able to even loot him after he died.

Kind of annoying on that last part but w/e it was fun. xD