I agree with you that QB is more impactful than RB on team success. Especially with the NFL the way it is now with so many advantages to passing that...
My guess is that situation matters more than total number of receptions. And that the difference in YPC is driven by big gains (i.e. that most plays...
FWIW, Joel is correct that Najee's 5.6 receiving average is ~ 46th in the league. The highest numbers are >12. If the "average" starting RB is about...