Well, for arguments sake lets review how many backs Saban has signed since arriving at Alabama; also interesting to note - in 2008 Alabama was actually a few spots over the NCAA mandated 85 scholarship limit. In order to make room Saban had to part ways with a couple kids, then he revoked a couple of the 1-year grant scholarship players back to non-scholarship status and also greyshirted a couple signees. Kind of goes to show you how what kind of flex you can get with the numbers (if you find yourself in the predicament we are in now or one that Saban was in when he arrived).
2007 - 3 RBs (1 was awarded a medical scholarship, 1 transferred to North Alabama his senior year, and the other RB transferred out to USF his Fr. year)
2008 - 3 RBs (1 was awarded a medical scholarship, 1 transferred his Fr. year before the start of Fall camp, and the other goes by the name of Mark Ingram Jr.)
2009 - 3 RBs (1 transferred to Nebraska after his Fr year, the other 2 are Trent Richardson and Eddie Lacy)
2010 - 2 RBs (1 transferred after his Fr. yr to Auburn, the other is still on the team)
2011 - 1 RB (He was arrested for possession and kicked off the team this year)
2012 - 2 RBs (1 is TJ Yeldon, the other is Kenyan Drake who was recently arrested - but is still on the team)
2013 - 4 RBs (all 4 were 4*s and in the Rivals 100. of the 4 Kamara is the only one no longer on the team)
2014 - 1 RB (5* Bo Scarbrough is having eligibility issues but may still have time to enroll)
Now compared to Tennessee in that same time frame;
2007 - 4 RBs/1 FB (1 turned into a LB (Vereen), Cooper the FB did not make much of an impact, Creer transferred to La Tech after his So. yr., Josh Hawkins left in 2009 I think, then Rogan was turned into a DB)
2008 - 1 RB/2 FBs (1 in Tauren Poole, Austin Johnson became a MLB, the other was Ben Bartholomew)
2009 - 3 RBs (1 in Bryce Brown who transferred to K-state in 2010, 1 in David Oku who transferred to Arkansas state in 2011, 1 in Toney Williams who transferred to Ball St in 2011 as well)
2010 - 1 RB (Raijon Neal)
2011 - 3 RBs (Marlin Lane, Devrin Young, & Tom Smith transferred to Tenn St this year.)
2012 - 2 RBs (Alden Hill was released from scholarship this spring & Quenshawn Watson gave up his scholarship, apparently college was not for him)
2013 - 1 RB (Jabo Lee DNQ, enrolled at Temple)
2014 - 3 RBs (all 3 are on campus)
I say there is absolutely no problem in taking 3 RBs in two consecutive classes, even despite our number crunch situation.