I've seen high level crystal/fury take out lower tier bosses during cutscene by themselves, it can make content uncompletable.
For a moment I thought you was talking about summons like in final fantasy. I believe they do. if not then they should.
It is good to see that 2+ years ago, people were still knocking threads off the list by creating threads complaining about this or that. At least it's consistent. ;-}