I wouldn't say Xe'ra is entirely without a point, either. Both in-game and externally speaking we (as players) are pretty easy to game - offer us loot and we'll burn down nearly any structure or kill any powerful entity to get a chance to roll for their belongings over their still-warm corpse. But that aside I think a lot of what Xe'ra is saying flies in the face of what both A'dal and Xi'ri were exhorting us to do back in TBC.
This, to me, opens up an entirely different supposition - that there are factions *within* the Naaru themselves, set to different goals and with their own agendas. I get the feeling that Xe'ra itself is something of a maverick, if not an out and out exile from the other Naaru. It seems to believe it knows better or different from its fellow Naaru, and where A'dal and Xi'ri were conducting a war on Illidan and his holdings in Outland Xe'ra is on his side or a believer in his "great destiny." I'm of a mind that neither camp truly knows the truth, and the final outcome will be somewhat different from what we're being led to believe (or that Illidan's "great destiny" will unfold in a way we don't expect).