Just to be clear, I was definitely not making any argument about the version of Collins that would have returned to Wake this year. Completely agree that Moore would have continued to develop, Collins would have played a lot of 4, improved defensively and continued to dominate on offense.
As you say, Collins regressed defensively and at least in my mind that regression was largely responsible for 2 losses that shouldn't have happened - VaTech in the ACC tourney and then K State in the NCAA. Don't get me wrong, it was fun to finally get our name called on Selection Sunday, but we were still just a fringe bubble team - we weren't really THAT good. Plenty of people posted at the time when we beat Louisville that in the long run it was bad for the program, and considering Collins leaving likely prompted the Dinos decision, it ended up being disastrous.
Our defense is better this year with no Collins AND no Dinos. Offensively, the spread between Moore and Collins (last year version) is 9 points per game. Let's say Dinos was a 12/8 guy for us this year which isn't much of a stretch - that's 7 points better than the disaster we have at the 4 in Thompson now. So even without factoring in defense, it's a 2 point swing compared to last year, maybe push it to 4 when you factor in some minutes distribution differences. So if we're 4 points better on defense we're probably a bubble team again.
I agree that the focus on Collins helped offensive spacing, but statistically that doesn't really translate. Craw is a couple percentage point down field goal wise, Wilbekin is up, Keyshawn minus the injury game is about the same... Moore demands a lot of attention down low even if he's nowhere near as productive as Collins. At the same time, he's been dominant defensively for long stretches ever since he learned to start going vertical against guards - he just gets hurt by stretch 5's and we have zero ACC quality 4's to slide down and guard them.
If Dinos stays I think the storyline this season is another bubble year and folks are surprised that we didn't take much of step backwards with Collins leaving - even if we didn't improve. And a loaded incoming class makes the trajectory a lot clearer. Instead Dinos doesn't just leave but waits until the last second to do it, Manning panics and tries to play his most talented guys regardless of position, and we get destroyed.