Wasn't sure if we should report or not, but thought I would just in case. Happened around 8-9pm (GMT-8)
Last night my guild went after Fennin Ro as we saw the Guardian of Doomfire up. Killed the first guy, which spawn the mobs along the path to FR. Killed the last grouping that would normally spawn the 4 (and some trash mobs) but they didn't spawn. On our way there, we only left up the 3 birds (which we've done before) and Blazzax the Omnifiend (this was the first time we left him up).
I didn't think there was a requirement to kill any of the other named, but just trying to detail out what we did. Just in case we went back and killed the Omnifiend but it didn't spawn the next group of mobs on the stairs.