Yes, having 2 number 1 backs will be work just fine...
I think we can all agree that we have one of the best run blocking offensive lines in football. Definitely top 3-5.
I think there is a great example of what this offense is capable out there. It is the 2009 Saints. The Saints won the Super Bowl as a pass happy big play offense, but they also ran the ball 468 times for 2106 yards compared to us running the ball 508 times for 2354 yards. They were six in the NFL in rushing.
How were they able to accomplish this?
Well they had Pierre Thomas, Mike Bell, and Reggie Bush... It was their offensive line that paved the way. Two time pro bowler Jermon Bushrod, two time pro bowl Car Nicks, 1 time pro bowler Jonathan Goodwin, 6 time pro bowler, 4 time all pro Jari Evans, and 1 time pro bowler Jon Stinchcomb. A lot of people wonder why the Saints aren't nearly as good now as they once were, and it is in my estimation that their offensive line got old/departed.
Anyways, if you look at their running backs:
Mike Bell - 172 attempts, 654 yards rushing, 3.8 yards per attempt, and 5 touchdowns.
Pierre Thomas - 147 attempts, 793 yards rushing, 5.4 yards per attempt, 6 touchdowns.
Reggie Bush - 70 attempts, 390 yards rushing, 5.6 yards per attempt, 5 touchdowns.
As you can see there are no world beaters here.
Can McFadden and Randle out run Bell and Thomas? Can Dunbar our run Bush? I think behind this offensive line the answer is yes.
Hell our wide receivers are definitely better than the 2009 saints as well. The question then becomes can our defense be as productive (key word) as the 2009 saints, and I think the answer is yes there as well. We played the Saints in 2009, and we beat them. We were a better team than them, and I think we're a better team than our 2009 team this year. That team got exposed by Minnesota because the defense was too inconsistent and the offensive line couldn't hold up against 4 rushers. Minnesota was simply a bad match up for that team.