Duke's OL was talented and that definitely helped.
But what I like to point out is, look at Duke's yards per carry compared to other NFL RB's in the same backfield:
2012 - Duke 6.8, Mike James 4.2
2013 - Duke 6.3, Gus Edwards 5.1
2014 - Duke 6.8, Gus Edwards 5.7
Duke was consistently better...