charred rivet
I'm not sure if this is a bug. But I don't think the bosses are executing their abilities correctly. As you can see, "Blazing Candle" should have a 10-second cooldown. However, as you can see in the image, the boss tries to use the ability multiple times. Or is this just a display error?
plain citrus
That AI pane is showing the configured attack sequence for the current phase in the boss fight. You probably want to add more uses of that melee attack into the sequence, so that the long-cooldown ability has time to cooldown before it comes around again. 🙂