For what it's worth, that's what the Hall of Gods is good for. Just practice the bosses you struggle with until you can beat them in Ascended, they'll feel easy in the pantheon afterwards. I found that to be less frustrating than grinding the pantheon itself.
By the way, did you find the uh secret "pantheon"?
EDIT: Oh, just saw they were complaining about the *colosseum*, not the pantheons. Yeah, the third one is a bit frustrating in that sense, and probably why most people just end up "cheesing" it.