WoWconomics

How to make money with skinning and the other two gathering professions is pretty straight forward. Kill things and skin them. The best place for you depends on a couple variables. One is your health and level. If you lower level of course you won’t be able to kill the level 79 mobs easily or at all.

There are many areas through Northrend where you can skin. The place I choose to farm is mainly related to what cooking food is the most expensive on the AH. This way I farm the meat (some go for up to 4-5g each) and leather at the same time. Some people think outside Warsong Hold is the best place to farm since you get Nerubian chitin (5g each on my server) and you’re relatively close to town. (Best solution if you can only do it for 15-20 min at a time so you spend less time in transit going back to town.)

I can update once I can find a set route that is best, but it is highly contingent on how many people farm on your server, and what extra bonuses you need from the mobs. (i.e. food, rep drops)

Outlands leather still sells, almost as much as Borean leather. So spending some time farming in Nagrand may prove profitable for you. The trick to farming lower leathers is to not flood the market, doing so will just lower the price. This also gives you the opportunity to get the talbuk that is purchasable through crystal samples/research tokens in Halaa.

The same can be done with rugged leather and thick leather (both around the same price as Borean and Knothide leather)
To sum it up, it may be more profitable to change your skinning type/location to not over flood the market. Everyone is farming Borean, so farming spots are competitive. Why compete for leather when you can go to somewhere lower where the mobs are easier to kill and the leather/meat etc are roughly the same price?

Patch 3.0.3