Interesting. My group had a harder time with oryx challenge. But then again we always had a hard time with oryx whether it was challenge or not.

It's not that hard. One guy in our group screwed up on the last damage phase so the aura just cycled through everyone while we burned down the last of his health. Golgaroth is a pain the ass just because they make you really go out of your way to do it which makes the fight take way longer and it's really easy to screw up. The oryx challenge is the easiest, but the whole oryx fight is just a pain in the ass because oh boy I sure do love doing the same boring thing sixteen times in a row.