Right now farming Exotic Leather is a bit like trying to hit a moving target. However, I will do my best to keep you up to date as blizzard seems to nerf known spots.
Best Exotic Leather farming spots for level 90s:
The Windward Isle:
This is the latest spot I verified for patch 5.2. Travel to the Windward Isle which is located off the coast of the Jade Forest and head towards the side of the island that faces the open sea.
You’re going to skin and kill the adult turtles and the yearlings you find there, and there are a lot of them. This is a daily questing hub so they are going to replenish quickly. The yearlings are level 87-88 and the adult turtles are level 90. There are other creatures guarding them so be careful. You need to be a level 90 and have decent gear to do this one. You are going to get very little if any scraps here, but you are going to get Exotic Leather and Prismatic Scale here.
One of the better places to farm Exotic Leather is in Vale of Eternal Blossoms. You go to Whitepetal Lake and kill the Stillwater Crocodiles. Now to see these you have to have done the introductory quests with the Golden Lotus so that you get their daily quests. You don’t need to be Friendly with them just finish the introductory quest chain with them so you get the dailies and you are good to go. (It takes 30 minutes to an hour or so depending on your gear and you have to be level 90 to get the quests.)
Best Exotic Leather farming spots for levels 86-89s:
A great spot for level 86s+ is the Grassy Cline in the Valley of the Four Winds.
One of the best places for those with entry level 90 gear and those that are level 86-89 is in and around the Torjari Pit in the Valley of the Four Winds. You’re going to kill and skin all the Bulgeback Tortoises you can find. My level 90 Skinner isn’t geared very well and other the odd and end I occasionally find I don’t plan to gear him up so this is one of the best spots for me personally to farm Exotic Leather as I can do a large pull. You can also do this spot as low as level 86-87, but with smaller pulls.