Fel Hide

Good spot I found happened to be at Arklon Ruins in Netherstorm. The fel hounds have a good drop rate of fel hide, and at the same time drop marks and fel armaments for Aldor. Within a half an hour I got:
9 fel hide
4 fel armament
15 marks
16 knothide
55 scraps

A good place to farm these is the Forge Camp: Wrath in western area of Blade's Edge Mountains (accessible only by flying). The wrath hounds there are relatively easy to kill, there's plenty of them and you don't have to kill anything else but the hounds.

I found the best place to farm these at higher levels is Karazhan.
1) Go into the level 70 portal.
2) Turn right and either nuke all the spiders or avoid them in the first room.
3) Mass pull the dogs and bats, AoE and skin.
4) Reset the instance.
I only get 1-3 Fel Hide per run, but it is fast, easy and in my control how fast the adds respawn.
There is also the added benefit of all the Heavy Knothide Leather I can make.
Lastly if you decide to also decide to do a loop of the servants quarters and pull all the Undead you can get 8-17 Soul Essence and Netherweave cloth which is needed to make Soul Cloth. Soul Cloth no longer has a daily Tailoring CD but is needed for the majority of high level BC crafting recipes.
With the changes coming to crafting in Shadow Lands expansion allowing you to up the item level of crafted gear some of these BoE crafted armors with multiple sockets might become extremely viable again rather than just for twinks.
Approximate average per run was:
~14 Knothide Leather Scraps
~106 Knothide Leather
~4 Fel Hide
~109 Netherweave Cloth
~77 Soul Essence
~3 Netherweb Spider Silk
~16 greens for vendoring or transmog sell
~312g RAW
~56g-Vendored Greys