There would have been zero need for a culture change in Diaco's first year at the helm (if he immediately followed Edsall) and there would not have been wholesale changes to the blocking schemes or defensive philosophy that helped limit our win total in P's first year here.
The only thing that I'll say against this is the fact that we had a pretty good defense in 2011 (
2012 was even better defensively, but 2011 was good). Would a transition to the 3-4 have been as successful as the Don Brown blitzfest with our defense? I don't know. We certainly didn't play a "bend but don't break D".
So the problem was on offense that year. But keep in mind, McCombs actually ran for over 1,200 yards that year as a freshman; the same amount as all of our running backs and QBs combined this year!
So that leaves the QB. That's what it comes down to. So if you believe that Diaco would have done a better job with McEntee and Nebrich than PP, then you can conclude he likely would have had a better record in 2011. If you don't, then you probably can't. The way he handled the QBs this year is not an indication that it would have been better.
Of course, if we focus on the original question of whether or not we would be better off today after 4 years of Diaco, then it's hard to conclude that we would be worse off. Not sure yet how much better we would be,
but hard to be worse...