this is a bit late and still heavily favors larger raid sizes
The soaks weren't a problem except on Jailer and Daddy D, and even then it's more because people would dispel too soon (soaks during massacre or mind control is BAD). It would have been better if the circles were more deterministic as to where they fell.
Dispel soaks are still going to suck for bosses like Painsmith, Sylvanas, and Holundrus. Depending on the timing, Anduin and Rygalon could be an issue too.
Definitely. It took quite a few attempts before my guild's group managed some semblance of regularity, but even then it was still along the lines of "you can do everything right and still fail" (at least for Sire Denathrius). We eventually defeated Denathrius on Heroic, but it was not a fun experience.