I just completed the quest for Dragonscale Leatherworking specialization. Dragonscale is really the only sensible path for hunters, since it's the only choice that deals in mail armor. And yet it seems like much of the gear you can make down this path is really designed with shamans in mind. Not that Netherscale Armor or Black Dragon Mail are useless, but I do feel like I'm going to be getting a lot less use out of my trade skill in my post-40 life.
There was a lot of conflicting and misleading information about taking this specialization, so I'd like to relay what I found. What follows is, naturally, relevant to the Alliance quest-giver.
First off, you need to be level 40 -- not 35! -- and have a leatherworking skill of 225. At that point you can accept the relevant quest from Peter Galen, Master Dragonscale Leatherworker. (The Wild Leather quests in Feralas are not a prerequisite for taking Dragonscale Leatherworking as some people claimed, though I believe it is required for Tribal.) Peter tells you to bring him 2 Tough Scorpid Breastplates, 2 Tough Scorpid Gloves, and 10 Worn Dragonscales. I collected my Scorpid Scales from Tanaris, and my Dragonscales from the dragonkin in the Wyrmbog outside Onyxia's Lair in Dustwallow Marsh. However, any or all of these items can be bought from the auction house if you prefer not to bother with producing them yourself. For the Tough Scorpid items especially that might not be a bad choice, as the pattern for both items comes from drops, not trainers.
Once you've collected all the quest items, take them to Peter Galen. Peter is in Azshara, a place I hadn't been to yet. I flew into Astranaar and rode east along the road, stopping just across the border in Azshara to get the flight path. Peter himself is almost directly south of the Ruins of Eldarath, and just a bit east of where the path cuts into the north edge of the Forlorn Ridge on the map. (His coordinates are 37,65.) You can reach him without encountering any mobs by cutting through the Forlorn Ridge at the point where you see the Horde watchtower. The tower is abandoned, so you won't be accosted by Horde NPCs. Just cut up through the path, into the Ridge, and travel east until you see Peter's tent. If you're having trouble finding him, turn on humanoid tracking. From there just hand in your goods, and that's it!