I usually try and avoid a QB/WR combo. For my comfort level, it's a little too risky...to many eggs in one basket. If the QB has a bad game, it doesn't bode well for the receiver.
I've never thought about the QB/RB combo, but given the right high-powered offense, I can see it being very advantageous.
RB: R. Rice, CJ Spiller
WR: AJ Green