It poofed with no experience when we killed it 11/26/2010, was annoying almost as much as the fact it casts the deal that drops agro. My guess is we killed it right as it casted it even though the wizard in our group got the kill shot so it wasn't like it died to a dot.
Killed it last night and got the Axe, I'm guessing it's just really really bad timing on when he does that goofy deagro effect. So he can be killed, with a bit of luck.