I made this Nether Dragonscale farming guide to help out players who want to farm the leathers instead of buying them from the Auction House. There aren't that many mobs that drop Nether Dragonscale. The three places below are basically the only places where you can farm Nether Dragonscale. The drop rate is the same at all three places, so it really comes down to your gear/class/level which place is better for you.
There were no major changes to Nether Dragonscale drop rates, so this guide can be used for Burning Crusade Classic (TBC) and Retail WoW. But, if you play Retail WoW, you should learn Outland Skinning from Seymour in Shattrath City before they start farming, or you will get fewer leathers.
Blade's Edge Mountains
My favorite place to farm Nether Dragonscale is at the Singing Ridge in Blade's Edge Mountain. The Lesser Nether Drakes are only level 66, so they are pretty easy to kill.
If you are Friendly and above with Netherwing, you can still kill them. All you have to do is open the reputation tab, click on Netherwing and check "At War". Once you have done that they become neutral to you, making it possible for you to kill and skin them. You will NOT lose any reputation.
Just like in Blade's Edge, once you are friendly with the Netherwing faction, you can't kill these guys anymore. You have to check "At War" with the netherwing faction if you want to farm these.
You can also farm Enslaved Netherwing Drakes and Enslaved Netherwing Whelps at Dragonmaw Fortress in Shadowmoon Valley. The only downside is that you will have to kill many other mobs guarding the drakes, so you will waste a lot of time.
Once you complete the Netwerwing questline, you can't attack any of these mobs!