Ive just cleared the area only 1 time and droped for me.. its a matter of having luck.
Well my stategie was not zone in with my shammy but only with my ranger. and when drops any then zone in and loot with my shammy.
I had a feeling that when i zone with my shammy, the game should making my shammy stay there for a long time.
In this case i was right about it.
I hope this helps a little.
Bowandarrow 115 Ranger on AB Server