I have some of the same concerns. I understand what others are saying to refute the size issue but if these guys ran 4.4 in the 40 or had some special skills it wouldn't bother me as much. The problem is that many of these guys are being put into different positions that what they were originally. Some, who may have been at TE may be getting put at OT (Windsor) or Te from WR like Aubrey or LB from SS like Accime etc.... Guys like Fleming have a lot of upside because he has a good blend of skills and his frame will support him getting in the 225 range while still keeping his speed and I think the same holds true for several of these other guys.
The area that size worries me the most is DT and LB. We do seem to be a little thin at both positions and we've gotten blown off the ball for as long as I can remember so I'd like to see some meat eaters get in the middle, sorry Kevin Foote....