I would agree with you on that as well. I personally felt he needed to move the ball through the air. The slower ball was his only real variation. I would wonder if this same point is why Gurinder Sandhu has not been given a new contract either.
I tend to think one of Faulkner's main problems is that earlier in his career he got pigeonholed in to the "finishing" role in ODI and T20I cricket, which ended up also hurting his red ball cricket. His injuries have not helped this though.