As many others i have also been using a gorilla for leveling. But i have chosen another spec. 31/35/0 (i'm currently at level 75) http://www.wowhead.com/?talent=cVbhdggR0zZ0eV0RVz...
This makes my volley stronger and uninteruptable. And with the new dragonhawk i dont get too much trouble with mobs hitting me, since i dodge a lot. with this spec i'm able to kill multiple targets with ease, and also keep the speed up when killing one target at a time if that is required.

If I happen to do the aoe trick, I simply switch to viper when looting and my gorilla is rounding up more mobs. this way i got full mana bar when my pet returns with new mobs for me to volley :D

Basically, I use volley if i got 3 or more mobs, i mean, critting for 1900 each tick, on all mobs(!) who can resist that?