I disagree with your assessment of the defense. I think you yourself said a few weeks ago that the game of football has changed and it's about scoring lots of points now. Clemson - LSU and recently Bama - Ol Miss, Bama - UGA being prime examples. All but Ol Miss have elite defenses yet they gave up a zillion points. The magic number last year was 31. If we'd scored just 31 points, we would have gone 12-1. The defense was not the problem. Is the D elite? No, but it was good enough to win 12 games if the offense had pulled its own weight.
In terms of recruiting, if you talked to me before the Clemson game, I'd have been highly critical of the talent at LB. But I saw a ton of promise in Brooks and Flagg the last two games. They should settle the biggest issues at the LB position this year (I am bullish on TAC and Huff as well). Granted, McCloud is a liability, at LB or striker.
Novels have been written about Rumphs bad recruiting. But credit where it's due. Couch erased Pitt's WRs. Blades is a gem. Dunson flashed as well. We definitely need to improve there, and I would not be surprised if Diaz makes a move to upgrade from Rumph unless he pulls some miracle and lands an elite CB. Frierson is doing well at striker, Hall has disappointed.
Safety is a mixed bag. Diaz brought in Bolden. He's going to play on Sundays. Carter is a knucklehead at safety, but I believe that if Avantae Williams was healthy, he'd be taking a lot of Carters minutes. I think Diaz also recognized that we've been weak recruiting at safety, and now we have an incoming 5 star, maybe the best safety prospect in the country. Williams and Williams have unreal potential.
All in all though, the defense has been good under Diaz's tenure. The talent infusion next year is going to be fun to see.