As stated above. 20,30 has a MUCH higher droprate. I killed about 16 for my first 2 before getting pissed and looking here. Once i did i tried that spot and got the last 4 in 6 kills. So basically, go to 20,30 and it will take you 5-10 minutes.

And if killing 10 or so for 6 is too low a drop rate you shouldnt be playing this game. Its not like there are very many quests with 100% droprate so get used to it!