I shall test for science!
Edit: ...assuming I can find where the silly thing starts -_-
Edit 2: I wonder if this is NYI. I have searched all over the Shrine, all over Stormwind (including warrior trainer), and even searched the Timeless Isle and did most of the intro quest chain. Ive killed stuff in case this started from a drop. Did a macro so I could spam targetting Gauros and Wei Wu and the three beast names. Nada.
Edit 3: Found more about it. The search continues! http://ptr.wowhead.com/quest=32995
Edit 4: Gauros Earthshatter is in the Horde Brawler Guild arena, but no quest without the entry. The way this reads, its "covered in dust" makes me think you find it, verses it being a drop. Also these entry quests are horde side. Couldn't find one for Alliance side. Still appears somewhat NYI or maybe starts in Siege raid, since one part requires 100 relics "from the bosses of xxx."