I tried to find some more efficient way of doing this and was kind of surprised by the result.
Here's the percentages for different mobs:
Oracle - 6%
[npc=182430] or [npc=182392] - 8%
[npc=181403] or [npc=181406] - 9%
[npc=181407] - 8%
[npc=181412] - 9%
So, from a time perspective, by far the fastest way to do this is to hunt down those big groups of non-elite [npc=181407] and pull the entire group and kill them all.
One thing you have to be aware of though is that due to bad design, all your helpers will disappear immediately when the quest is done. So you can be in the middle of killing 10 mobs and if the quest finishes, you'll be on your own. More bad design, but is anyone surprised at this point?