Just like you need to give a first-year head coach several years to recruit the right kids, teach the system and get them all working together, the same is true of a new DC. I was not happy when RR hired Scott Shafer. I mean, if you are looking for a DC, who thinks of Stanford? But I did not think it was fair to cut him loose after only one season when the offense did everything possible to keep giving the ball to the other team as quickly as possible.
Robinson deserves a chance. He has a very good track record as a DC. He seems like a decent, honest person who doesn't cheat (if he was cheating at Syracuse he was doing it wrong). And I think that many of the problems you see as "scheme" failures might just be fallout from the fact that the kids are still learning the system and, therefore, are not always in the right place and do not always have their assignments down. Add to that the lack of depth and size, both of which should be corrected over time, and you have a perfect recipe for a mediocre defense.