this guy is an interesting encounter. you have to kill his pieces to kill him. I did it with my necro pet and recieved no loot or exp so i probably did something wrong.
I also had a problem with the encounter using my necro. 42 necro with lvl 34 bot..went through my first time and used the deathsight lifetap to kill the pieces and wound up with nothing. Went through a second time just having the pet melee the pieces and I was able to get loot. I'm guessing that casting through the pet causes some wierd bug that doesn't grant you credit. I'll be doing the melee route from now on to be sure.
Ok, I just finished my 3rd run having my necro pet melee the pieces, and I got jack squat like the first time. Either the mob is bugged, or necro's are kinda hit and miss with this encounter. I've sent an appeal, we'll see what comes of it.