Hyperbole on my part, but the fact remains that Bama pulls in more guys at those positions than can possibly play over a 4 year period.
The little sisters of the poor (read: us) would like one of those stud RBs please, Mr. Saban. You have lots to spare.
I'll eat my hat if this kid doesn't transfer this season:
http://247sports.com/Player/Altee-Tenpenny-11893
Also, I'm not sure we really overstock QBs like you suggest we do:
2015 (1) Blake Barnett - 5*
2014 (2) David Cornwell - 4*, Jacob Coker (x-fer)
2013 (2) Cooper Bateman - 4*, Parker McLeod - 3* (already transferred out)
2012 (1) Alec Morris - 3*
2011 (1) Phillip Ely - 3* (transferred out)
2010 (2) Phillip Simms - 5* (transferred out), Blake Sims - 4* ATH
2009 (1) AJ McCarron - 4*
So, pretty much every year we've only signed 2 QB commits, with the exception of 2013. Blake Sims was recruited as an athlete/running back not as a QB.
The reason we took 2 in 2013 is because our QB depth was atrocious. We had: McCarron (Sr.), Sims (Jr.), and Morris (RS FR) on the roster as scholarship QBs.
Following the 2013 season, our QB depth was again thin because McLeod was looking to transfer out. This gave us: Sims (Sr.), Morris (So.) and Bateman (RS FR) as our only scholarship QBs.
We're only taking one QB this season, so, assuming no one transfers out, our depth chart will look like: Coker (Sr.), Morris (Jr.), Bateman (So.), Cornwell (RS Fr). and Barnett (TR FR). That's essentially 1 QB from each of the past 5 recruiting classes represented (counting 2015).