I have done this zone several times, and followed the walk through thinking I have done something wrong. For some reason Tribunus-Prime Hagandr never spawns after the other named are killed. I am trying to finish the signature quest and it is getting annoying. Is it broken, or is there something I am missing. This is the heroic zone, not the raid zone that requires a scout with the class buff.
Found another thread about Throne of Storms, took that advice and got Tribunus-Prime Hagandr to spawn. Guess those bosses needed to show off their tricks before the big boss will come!