To be fair, Gillisee did get 5.7 YPC on 100 carries (leading the NFL in YPC), and this on a team with no discernible passing game, against teams routinely stacking the box against him/McCoy. If that isnt talented, I dont know what is.
Yes the offense goes through Brady, but that system seems to get the best out of every player they bring in. If they can get MORE out of Gillisee than he has already shown, he will be a beast. If he can average even 5ypc (which is considerably lower than his 5.7 average last yr) with the amount of carries Blount got last year (299), he would be just short of 1500 rush yds. With Brady taking the pressure off of him, the sky is the limit.
But the rest of them are, like you said, products of the system. I would even go so far as to include White as one of the system players, as I dont see him as an all around good player that could succeed on any team. Hes a good west coast 3rd down RB. He's never going to be a workhorse back. Hes another interchangeable tool in the Patriots toolbox, much like Shane Vereen before him.
The Pats do a tremendous job of getting a bunch of different players who do one thing really well, and then they rotate players in to fit the gameplan they need for that specific week/quarter/drive. They play to a players strengths and never really ask them to do something out of their comfort zones. Its very frustrating as a Colts fan to watch this, as we seem to constantly try to fit square pegs in round holes when it comes to our players.