I don't know why this team isn't running more 2 RB sets, honestly.
You could still have 3 receivers out there...take your pick: AJ, OD, Graham or Walter or Posey or Casey.
With a 2 RB set, you could do sooooo many things to confuse defenses:
(A) You could run Tate
(B) You could run Foster
(C) You could fake to either of those guys and run a playaction off of it.
(D) Both guys could be a receiver out of the backfield
But hey, that'd be too difficult. Not enough time for the genius Gary Kubiak to install that sort of high-level "trickery" and make sure his Pro Bowl caliber QB, RBs, and OL could handle the duties.
No, what REALLY has been selling like hotcakes is to have only 1 RB, and then (hee hee hee!) motion that 1 RB out into a WR spot prior to the snap! OMG! The defense won't know what to do!