Yeah, I'll be completely honest with y'all. If Gus had made this hire, I would not have been happy. Belichick and Saban's (earned) credibility, however, leads me to believe that there's something there I'm just not seeing.
I agree with you that the Saban/Belichick stamp of approval is the greatest comfort, but IMO, there's more than that. 3 different NFL franchises wanted him as their OC. And Brett Favre had one of his best seasons as an NFL QB - and this was late in his career, with the Jets. And though the team records were poor to bad, the HCs were bad and there was not 1 starting quality QB, in fact most of them were not even NFL backup worthy. I do think the "...a part of 5 SBs" is over stated, but he has been a part of a committed and smart staff. His rep is that he communicates well with the players and staff. The main personal trait is that he appears to be smart, coming from that staff.
I don't think Saban settled at all. In fact, by the last week before the hire was made, he was who I personally wanted because it was clear how badly Coach Saban wanted him. Bama was waiting on Daboll, not the other way around. I can think of very few college OCs I would rather have had. Only Dan Enos, Lincoln Riley or Kevin White might have interested me more and that's primarily because of a proven track record with a balanced college offense. I had no desire for Kelly, Helfrich, etc. IMO, he starts off in the SEC only behind Enos and maybe Canada.
This also seems to signal, not a full retreat, but a move toward the pre 2014 offense. It's hard to abandon the QB runs and RPOs because they give Os such an advantage; also, it's easy to overlook the 1 man advantage with the QB runs. It's good to be able to practice against such offenses on a regular basis. But Bama has the talent to run a NE type "pro spread", though they'll never have a QB to run it like Brady does. They are smart enough to adjust.
I agree with others that the idea of a "safe hire" was not a factor, in fact, he could be gone after next year, assuming he does a good job.