To get to the quest giver, you have to get into the wailing caverns in a special way.
When facing the entrance to the instance, (while still outside of it, it should say you are in the barrens) you should see that the entrance looks like a face. The questgivers are in the left eye. To get there, climb up the mountain, drop onto the head, drop onto the brow, drop onto the nose, face the instance, and go into the eye on the left

Here's how I did it:
Go in front of the summoning stone and there is a ""path"" leading up It looks like a T intersection. Make your way up, take your left, and you should see the ""top"" of the cave. . Look down and there's a ledge that looks like an arrow ^(aka the nosey). Jump on it, and face the other way. There are two ""eyes""(call them whatever you want). Jump on the Left one and if you made it, make your way in. There's 4 NPC's. You get two quests here. There's also a leatherworking trainer and a vendor who sells some things(mostly visited to buy the limited supplies of 2 deviate leatherworking plans).

For Deviate Eradication:
1. Deviate Ravagers- When you arrive in the instance, the first mobs are Deviate Ravagers/Guardians. If your group is after lady Anaconda, you'll find you are travelling in a huge circle above the ""river"" at the bottom. Usually you'll already have 7 kills already before you go down, so don't wry bout it too much.

Edit: They are pink raptors, while guardians are blue.
Also, don't stray away from your group just to pull these(if you are in a group)! Usually they'll have a Deviate Guardian with them, and when dying they'll give a shriek(emote), and Mobs near them will aggro you. The range is actually farther then you'd expect.

2. Deviate Vipers: When you get to the river, make your left. If you have a map of WC this will lead to Lord Cabrahn(fanglord). On your way, there are plenty of vipers. You should already have 7 kills before you reach him, so dont fret.

3. Deviate Shambler:
Back to the river. Instead of left, make your right. If you're looking at a map, this leads to the last 2 fanglords. There's a huge pool on the left, but that's for jumping after Verdan the Everling is killed. No point going there. Turn right again, past the crocs and up the ledge. There are LOTS of these, so dont' worry ""Plz kill all shamblers in sight, 7 kills is alot!""

4. Deviate Dreadfang:
IMO, these take the longest. These guys turn up after the third fanglord and on your way to Lord Serpentis. There should be 7, but kill all of them just in case. Sometimes, there are Deviate Venomfangs, but these are not the ones your looking for(they are green, and the dreadfangs are kind of blue-gray).

Hope this helped, and not too long

It does also count towards Loremaster of Kalimdor.

Completing this quest yields credit for Kalimdor Loremaster (for Alliance, at least). It's worth resetting the instance to get the remaining Deviate Dreadfang count taken care of if you're going for the Loremaster achievement.

For some reason the built-in questgiver is telling me that these guys spawn in Stonetalon Mountains. They obviously do not.