If what you say is true, we will be face to a totally unknown kind of boss. I only see two ways it could be. First the boss bonus won't be the same kind, mean a sphere you 're kiting and a boss making AOEs every 30s. Or the second way is that if it's on Calphayus room, and if the fight still be the same as the 2 others, we should be transfered in a parallel dimension where we would have the possibility to kite him. Here would be a good point to know, what kind of 3rd boss bonus is it...