I never really camped..when I was bored I would tele out there and check to see if he was up..I killed him prolly 10 times over about 6 weeks and I never got drop..
If you spent the time you camped him xping you would most likely be past the lvl where thrak is even worth it lol.
Terrible drop rate combined with stupid pop conditions make him a gaint *** of a bird.