In my opinion STV lvl 41 gorrilas are the best!!! PEOPLE are killing them all the time and u can just skin away for heavy leather and sometime thick leather WOOT
STV for sure. Just follow the people around who are doing the Gorilla quests just outside of Booty Bay. You will get all the leather you need without having to kill a thing.
Here is one for you.... Duskwood. The first consistant HL drops I saw were from the Worgen south of town. Lots of them to skin for free and if you are higher level, you can mow them down like wheat before the scythe.