Honestly , I disagreed with part of the premise, since I believe that CD has been an absolutely essential part of Geno's success. They have been the perfect complementary pair. I don't think UCONN or Geno would be where they are today without her.
Especially in the past, when Geno was a lot more in-your-face and explosive, CD was a most necessary counterweight. Good cop / bad cop, or whatever you want to call it, but much more than that. (This not to say that Geno has always been 'bad cop.') Geno himself has admitted many times the almost neurotic fear of failure that has driven him for much of his career. I think it's always there, though it's less obvious these days. Geno has also said he realized some time ago that he "can't control everything" and I think this is part and parcel to letting go of that fear a bit.
Anyway, partly because of this fear, Geno really, really, really pushed his players for years and years as the program took hold and success started coming. Of course he still pushes a lot today, but I don't know if that much pushing would have been possible in the past over the long haul, the way he did it, without the cohesiveness provided by the unique culture he and CD built together and without CD as a complementary force. The culture did not come about just because of Geno. There are lots of examples of head coaches pushing people to the limit and past the limit to the point where the program fractures because the other essential aspects aren't in place. It's really all about psychology. The players can't think that "it's the coach or them" and they're on an island. The culture has to inculcate everyone with an extremely strong sense of shared responsibility and shared sacrifice to where they realize somehow they can make it through together, and that 'Coach' is not the only source of the crazy expectations. You're at UCONN now - more is expected. Clearly Geno and CD recruit tough-minded players, but that's not enough. As the words on the wall say, "Champions aren't born, they are made here."
As a tandem, I would put them in the conversation of the greatest ever because the biggest part of coaching isn't X's and O's, it's program-building in all its many respects. And program building in years 1, 2 and 3 means the X's and O's conversations can take place at a whole different level by the time years 10, 11 and 12 roll around. Geno is truly awesome--and a genius--but the credit goes to both of them.