Cobra Scales

I found that doing the escort quest made farming scales a lot easier. The NPC you're supposed to escort is tough enough to handle anything that shows up, and once you've reached the water spirit the NPC is literally escorted by a small army capable of handling not only the mobs in the cave and the scripted Assassin-type mobs, but also any other mobs you pull to them. You won't be able to loot (or skin) any of the mobs that the NPCs do more damage to than you do, but you can use them to clear out all the nagas while you focus on killing cobras. It makes things much faster and smoother, and you

The Coilskar Cobras definitely drop these, though the drop rate is pretty low. There is a cave you can enter and farm them, though you'll also have to clear the naga. From just my experience, I killed and skinned about 45, and got the two scales I needed. There is also an easy escort quest in the back of that cave that will give you about 23g and a decent green.

Twilight serpents in Nagrand were the easiest to farm. A lot of them around,by the time you kill the last one in the area the first one you killed would have spawned again.