Yeah, perception is perception. People who don't care for Duke's approach are going to use guys like Thomas as evidence that we don't utilize our bigs properly. And not getting more out of the Plumlees is a question mark.
That said, I don't think Mason should work on his perimeter game. I think he still has enough work to do on his post game before worrying about developing a perimeter shot. I'd argue that his first 1+ years were lost to some degree because he spent too much time playing outside in (I remember some posts during/after his freshman year in which people were suggesting he'd show more shooting range than McRoberts) rather than learning how play closer to the basket.
If he decides to come back, I want to see him work on polishing his back to the basket game and his overall instinctiveness/fluidity in the post. Master that, and he can play with anyone in the league. Without that I think the Jeff Foster comparison isn't too far off.