Apparently this quest is broken. After very carefully not taking Yoon's quest, I took a death knight through all the rest of Pandaria's 5.0 zones and factions, unlocking dailies (and in one case getting exalted and finishing the storyline). I filed a ticket on my way to doing the Order of the Cloud Serpent, as I didn't think Sunsong Ranch had been endgame content, but I was fairly certain the serpents were. The first GM indicated that I did indeed lack the Order of the Cloud Serpent. So I finished their quests up to unlocking all the dailies, with only the final exalted quest remaining. Back to Dooka... no quest.
I re-opened my ticket. The second GM, after a response that indicated GMs shouldn't have to deal with such nonsense, dropped my character on an NPC and said I needed to finish opening the Vale, specifically to complete quest The Guo-Lai Halls. Um. Sure. That quest was removed in 5.4 when the Vale got sha'd.
After my third round on this ticket, the response is that they don't know why it's not showing up so just file a bug on it and hey I dropped you on Yoon so have a good time. My completionist soul is crying, but I suppose I've done all I can.