After trying it out on a training dummy for some time I have to say it is a bit too much. You can pull it off when hitting a training dummy and constantly watching timers/procs etc. If it was a difficult raid boss then you obviously could not use all your concentration on your rotation anymore and it would collapse.
I am wondering what they are going to do to make it easier. It feels like only an ogre with two heads can watch the fight and all the timers/procs at the same time.