What is wrong with that stupid demon brick (LoV #12)

[Espritduo]

Were there other minions around him? If you send a swarm of your minions at the brick while it's at an aetheryte with other enemy minions, your minions will just attack whatever is closest to them, the Demon Brick usually being left out if there's a horde there. Try positioning your minions so their range of attack has the brick right in front of them and the other enemy minions on the other side. I had this trouble both with the brick and other bosses and had to re-position my minions to "persuade" them to attack the right target.

[Atoli]

Were there other minions around him? If you send a swarm of your minions at the brick while it's at an aetheryte with other enemy minions, your minions will just attack whatever is closest to them, the Demon Brick usually being left out if there's a horde there. Try positioning your minions so their range of attack has the brick right in front of them and the other enemy minions on the other side. I had this trouble both with the brick and other bosses and had to re-position my minions to "persuade" them to attack the right target.

I had the brick alone in front of the last broken gate. He didn't move, he never lost HP. I tried countless times in those 5 hours and nothing ever happened, that's why I got so frustrated.
I tried again the same day in the evening and it worked just fine (and I went on to beat all the trials the same evening, never having the same problem as during that trial in the morning). Thanks for being the first answer that actually deals with my problem instead of giving out strategies that I didn't ask for xD
Since no one else seems to have encountered the same problem yet and it obviously isn't rooted in the brick only being vulnerable to a certain minion, which was my first thought about this, I'm 99% sure now that it was a bug (especially since it worked just fine later after logging back on, without any change to my strategy). I'll file a report, and this thread can be closed.

Thanks to everyone for trying to contribute and help