For comparison's sake, here are some physical stats:
Gronk: 6'6", 265 lbs, 4.68 40-time, 23 bench press reps
Williams: 6'2", 245 lbs, 4.59 40-time, 20 bench press reps
Hooman: 6'4", 264 lbs, 4.74 40-time, 25 bench press reps
Mulligan: 6'4", 248 lbs, 4.89 40-time, 34 bench press reps
Develin: 6'3", 245 lbs, 5.03 40-time, 39 bench press reps
Hooman and Mulligan are what they are: traditional blocking TEs. Develin has flashed the last couple of games, he's a weight room freak, and I love the shoulder pads, but his 40-time probably prevents him from playing as a legitimate receiving TE.
Williams is far and away the most athletically gifted TE on the roster now, but he feels like more of a special teams contributor than a legitimate offensive weapon.
EDIT: For comparison's sake, Blount: 6'0", 250, 4.59 40-time, 18 bench press reps. He's just not big or strong enough to be a TE.