I dunno about the mismatch rotors. I've run a S4 flywheel on an S5 (out of necesity for a breif period of time) and even with that I didn't really get any vibration you could detect just running the car. I'm sure it was wobbling due to the rear bearing being shot after
but no noticeable engine vibration at all. And I'd think that difference is greater then one wrong weight rotor......but....its uncertain.
Usually a heavy vibration like this is a misfire - which system its related to though I can't say for sure but would bet ignition.
Have you tried rotating the CAS with it runnning and revving and see if gets worse or better?