I am aware of that, but after some point for me the locust just didn't stop spawning, before I finished one wave, the second one was already there. And in case of inconsistency, sometimes the swarm despawned before my next attempt, sometimes not, also sometimes eidolon would go back to sleep, and sometimes he threw rocks at me before I even got into the arena, on one attempt he even killed me before I had chance to do anything.
I guess I'm just bad at combat in this game