The problem is not supervision. The problem is greed. Anybody could provide safe anesthesia with two rooms running, even with mediocre CRNAs, but no, we do 3 or more. That's like taking care of 5 times more ICU patients: just a subpar quality race to the end of shift.
No truly good doc will enjoy this. Too many balls in the air increase the chances that one won't be caught in time, sooner or later. It's just assembly lane and shift mentality, not quality care. But, hey, we're producing all that profit, so it must be good medicine, right?
Much better to sit in a room and think about how I could improve the care of this patient, or the next, or the one after that, or just read stuff to improve the care of the next thousand. Great docs are not the ones who just do, do, do, but mostly the ones who read, read, read, do, read more. Otherwise one just ends up being like an old CRNA, all monkey skills and experience, pretty much a one/few trick-pony.
I am sorry, but I will never believe that quality of care can happen with 3:1 supervision, except with very long cases, or very good midlevels (at which point it's basically independent practice with a firefighter preop monkey doc as resource).