I'm not sure if people follow up on the hidden skins or have read the recent post on Mmo-champion, but some stuff has been discovered for a variety of classes regarding hidden artifacts. A lot of stuff has been datamined for the Corrupted Ashbringer, and it seems to tie with the old "real way" to get the ashbringer. You need some books and a whole lot of other stuff like Nefarians head. Now you can't sell nefarian's head, but you CAN sell the books.
The books are: Nat Pagle's Guide to Extreme Anglin' and A Thoroughly Read Copy of Nat Pagle's Guide to Extreme Anglin'.
The first book can be looted from DM in A Dusty Tome. They're laying on the floor around in DM. If you want then you can use Yeti Radar Bot to find them. There's a great comment in the comment section on Wowhead stating where to find the books on the ground, and there's a map with coords in the link too.
Known Spawn points:
Near the southwest corner in Fengus' courtyard
Under the ramp near which Slip'kik patrols
Directly behind the Observer
Near Lethtendris (Did this over 100 times, saw 10 Dusty Tomes, spawn rate is 10% so far)
In the big drop down area at entrance, middle along the east wall.
North end of the ledge (directly above the big door), between a pack of lashers and a big tree.
In the Shrine of Eldretharr (End of the instance, by the root that Alzzin the Wildshaper walks up to).
The Southwest corner of the first courtyard
I'd suggest going DM East since there's most spawn points for the book. You can't go DM West anymore and then run through the tunnel to DM North like in the old days, so you gotta run all the way back or log out for some mins and then in to find yourself outside of the instance.
The second book drops from player corpses in Alterac Valley, which will require some PvP farming.
Both these books sell like crazy to paladins with lots of gold and who's lazy. On Silvermoon EU the one from DM sells for 30-35k (fell a lot last night) and the one from AV sells for 125k.