Black Crow map boss Unkillable, can't complete map objective

I'm currently stuck in a t15 map, objective "Kill Black Crow." Got him down to half health and now my crossbow skill won't auto-target him and does zero damage when I do manage to him. He is not transitioning into his 2nd phase. Tried exiting map and re-entering, logged out, exited game and re-entered. Still stuck. Can do no damage to the boss so I guess I'll have to die and lose xp to exit the map.