It was in part Vilma's fault. The d-line had nothing to do with his problems shedding blocks from guards last year. Vilma struggled because he was too small to take on guards. If you watched him play, you would have seen that his size was a big problem for him against the run and rushing the passer. It wasn't all the d-line's fault.
Also, I don't buy into what Belichick says before the draft unless he follows through.
The fact of the matter is the Pats always go for bigger LBs. The OLBs are almost always over 260lbs (Colvin the lone exception) and the ILB always hover arounf 250lbs. Because of the two gap scheme, it makes it hard for smaller LBs to work well in our system. Size, instincts, and smarts are far more important than speed.