I think the best place for thick leather is the Badlands, You can combine leather farming with a chance on a rare pet. You can get here fast by using the portal to Blasted Lands and flying to badlands.
The mobs you will be killing are called Nyxondra’s Broodling
This is what you will be skinning, you will mostly be getting Thick leather and some Rugged leather which sells for a high amount on my realm as well.
1 – 6 Thick leather 77%
1 – 6 Rugged leather 20%
1 – 6 Thick hide 3%
It might take two or three clears to get a hang of it but as the whelps are ranged you ideally don’t want to one hit kill them, if you can 2 hit kill them they will die in a less spread out area. I did this on a DK and hunter and found it a lot faster on a hunter. This spot is amazing because of the fast respawn, and it is very quiet. You don’t get many people randomly flying over this spot or levelling here and the added bonus of a chance on the dark whelping is fantastic. If you have mining on your skinner there are 3-4 nodes and you can pick up some mithril ore while farming leather.
An alternative is Un’Goro crater the raptors in the south east, you can take the portal in Dalaran to get to Tanaris very fast.
The raptors are spread out a little more than the whelps,if you keep an eye out you might get lucky and pick up a raptor pet from the nests scattered around this area. The raptor pet is called Ravasaur hatchling.
What is the price of thick leather on your realm?