I think Geoff is a good coach- but I also think he is not very creative and I think he is a "pleaser"- see the 1A/1B stuff where everyone plays the same amount of reps. He couldn't make common sense adjustments- like expecting Zach Jackson to be Matt Wells instead of going to nickel.
A good defensive coordinator should have been able to scheme to cover our weakness- our safeties- by blitzing and putting more pressure on the QB rather than rely on them to make plays without any help whatsoever.
But I think Manny is going to be a huge upgrade because of what I just talked about- he can scheme around some of our weaker players. Which is probably why Coman suddenly looks a lot better right now. By disguising what we are doing and blitzing more- we should be more effective as a defense. Not to mention playing our stronger players more- like Chris Jones, Redmond, etc.