Kind of surprised no one's brought up Cut and Run. The mechanic is similar to Soar from Zurvan (untelegraphed attack, with the players needing to spread their player-targeted aoes into a restricted space with no obvious borders), and Soar was INFAMOUS. It's the mechanic that stymied several of the groups I was with, until I finally got my clear.

That said, while similar to Soar, it's not as bad. So while I'd rank this fight in the upper half of all Ex Trials, I wouldn't put it very far into the upper half.