Spoiler for those who haven't got past the titan runestones or haven't heard the Wrathion PTR files.
Upon bringing Wrathion the Thunder King's Heart, he eats it, at which point he gets posessed and speaks in mogu voice:
WE HAVE FALLEN. WE MUST REBUILD THE FINAL TITAN. DO NOT FORGET.
Than, during the Escalation storyline, we're introduced to Dark Heart of Pandaria scenario, where meet titanic watcher Norushen, who was responsible for guarding the container holding the heart of Y'Shaarj.
And now, with datamined files for Siege of Orgrimmar, we now see that he's a boss as well, but more in a style of Valithria Dreamwalker.
We do not fight him, but instead he blocks out the exits into a quarintine zone (much like in scenario) and than forces out the Sha corruption out of the players, creating the boss.
Than further, while facing the Sha of Pride, he helps players, by protecting them from corruption and empowering them with titanic power (probably much like Engine of Nalak'sha from Elgalon).
Putting all the pieces together, Norushen was created for sole purpose and empowered with ability of expel the sha corruption, he was set to guard the Heart of Old god, but Mogu, due to curse of flesh forgot about it.
If Norushen survives the events of Vale and is taken to Orgrimmar, it's likely he mite be able to expel Garrosh's corruption... that is assuming that Y'Shaarj's direct corruption can be dispelled, considering that he was unable to purge the poor gobline in the scenario nad we had to kill him instead.
This also puts into perspective as to why the mantid, kept attacking the lands beyond the Wall. Some of them (as proven by Klaxxi paragons) have been locked away in embers for countless eons and are probably aware of their former master's final resting place, which would also explain their presence in SoO.