Outstanding, thank you.
You don't need to be uber level to do this. I am farming it with a 23 Inquisitor and it is going really well. The Greedy Body Mutilation aspect (I believe) gives you a second chance at the good stuff also, because I am occasionally coming up with more than one piece after a kill. I have 12 pieces now in what I think was about 8 runs (sometimes kills netted me no set piece.)
After reading farther in to this thread where you say fewer hits and quicker time makes them drop more, I am just going to kill the bird; with a beefed up Cluster I can kill it about as fast as the 60 elf.
Edit added: There is some other unknown factor here. My 19 Seraph with ~10 in enhanced observation can 2 shot the bird with archangel's wrath (better than the inquisitor many times) but I still can't get a single drop from either mob. Once at level 20 and over 50% survival bonus, she is able to get drops now. It seems like about 60-70% of the time but I really haven't been doing the math.