User blog comment:Hawki/Legacy of the Void - Reflections, Ruminations, and an End of an Era/@comment-72.197.211.140-20151207032013

You know Hawki, with regards to "It was Ouros all along" and never was Tassadar, this would be slightly contradictory to the "Echoes of the Future" mission. In that mission, Zeratul wanted to know why were the Zerg altered and for what purpose. Yet "Tassadar" said he didn't know. This makes no logical sense if this was merely Ouros the whole time. As Rohana had said, most of the Xel'Naga did come to Zerus to find out what Amon was doing. Amon released the swarm and killed most of them. Now, let's pretend for the moment that Ouros was not among those who came to Zerus. Surely had to have known what was going on, as Rohana specifically said that the Xel'Naga had been rouse from their slumber and everything, and that'd include Ouros. If that's true, then even if Ouros had stayed at Ulnar, he would have known about it.

Furthermore, when Artanis and Kerrigan reached the Xel'Naga chamber, you could easily see the Xel'Naga had been killed by Amon (or his minions). Ouros was not among those killed, but we don't know for how long he had been a prisoner of Amon. If he had stayed at Ulnar the whole time, then Duran would have captured him for his own twisted intents.

But the bottom line is that Ouros had to have known what was going on, yet he didn't tell Zeratul. He didn't even tell Zeratul about Amon's name. Unless, of course, you're suggesting that Ouros kept things so vague for the PLAYER'S sake, so the PLAYER would be left guessing as to what's really going on.