A FB is needed in Daboll's offense, at least if it's anything like the Pats* system/offense. A FB generally helps a short passing game with blocking, as a receiving outlet, and to disguise passing plays with running formations. They are particularly useful in play-action for all 3 of those reasons.
At this point it would be too much of a hiccup to release DiMarco and pick up another FB or use a TE in this fashion, imo.