What if a boss had three attacks that could be silenced, if one is silenced then it would immediately start casting one of the others and if that one was silenced the third could not be. They would have various effects and the order would be random, and would also occur in conjunction with other mechanics. Essentially the party could choose what combination of mechanics they would deal with if they are quick enough.

This might be a bad idea, just a thought on a possibility for making the action be less of a QTE type of thing.