Can We Be Successful Not Drafting an RB Until the 5th Round?

Can we be successful not drafting RBs in the early rounds?  I did a couple of 12-team mock drafts to see what kind of team I could assemble if I didn't draft an RB until the 5th round.  In the first example I picked 6th overall.  In the second I picked 12th, meaning my 5th round pick came later in the second example:

Draft 1:

QB Ben Roethlisberger (PIT)
RB1 T.J. Yeldon (JAC)
RB2 Todd Gurley (STL)
RB3 Ameer Abdullah (DET)
RB4 Knile Davis (KC)
WR1 Jordy Nelson (GB)
WR2 T.Y. Hilton (IND)
WR3 Charles Johnson (MIN)
WR4 Pierre Garcon (WAS)
WR5 Kenny Stills (MIA)
WR6 Rueben Randle (NYG)
WR7 Marvin Jones (CIN)
TE Rob Gronkowski (NE)
K Stephen Gostkowski (NE)
DST Seattle Seahawks (Sea)

Draft 2:

QB1 Peyton Manning (DEN)
QB2 Carson Palmer (ARI)
RB1 T.J. Yeldon (JAC)
RB2 Todd Gurley (STL)
RB3 C.J. Spiller (NO)
RB4 Knile Davis (KC)
RB5 David Cobb (TEN)
WR1 Odell Beckham (NYG)
WR2 DeAndre Hopkins (HOU)
WR3 Allen Robinson (JAC)
WR4 Marvin Jones (CIN)
WR5 Rueben Randle (NYG)
TE Rob Gronkowski (NE)
K Stephen Gostkowski (NE)
DST St. Louis Rams (StL)

In each example I grabbed Yeldon in the 5th and Gurley in the 6th.  Had these been real drafts, I probably would have added Tre Mason in the 8th, since if Gurley can't go, Mason will have low-end RB1 potential.

In the first example, I didn't take enough RBs; I fell in love with all of the underrated WRs remaining on the board.  In the second example, I made sure I had two starters, one potential starter (Cobb), and two guys fully capable of posting RB1/2 numbers if their lead backs go down (Spiller/Davis).

In each example, I was able to snag an elite or near-elite QB, an elite WR with solid WR2s and 3s behind them, the #1 TE, the #1 kicker, and an elite or near-elite DST.

Every season, a sizable minority of starting RBs are replaced at some point.  So if you can wait until Round 5 to start drafting RBs, and are lucky/smart enough to get guys who should yield at least RB2 numbers (whether it's Yeldon or Gurley or Gore or whoever you think is underrated, then you should be able to compile enough elite talent elsewhere to keep you competitive.  And if the Knile Davis's or C.J. Spillers of the world (or whichever complementary back / handcuff you're targeting) is thrust into a starting role at some point, your roster will be stacked.

To be clear, I'm not recommending this approach above others.  But it's useful to understand how it could--*could*--produce a championship-caliber team.