Yeah, but don't you think a dude wearing full armor should be able to take a little more heat than, I don't know, someone wearing a robe and a sheep's head?

Haha they are magical space robes! Haha. Come on man, its like asking "how csn the monk tank more than the barbarian when he is just wearing. Robe and beads" Its not supposed to make sense, its a game for once. But the skills and abilities is what allows for such a thing to happen. Also, yes the warlock can be a tank, but he needs to be in yiur face for that to happen. If you space properly half of its abilites become useless

Dude just sell your copy of destiny because you know nothing of the game