couple of things,
Casserly specifically has seemed to do his best drafting when he has stayed at his position and picked the guy that they have liked at the spot.
Overall, at the top of the draft i think teams go more for homeruns than take the more solid pick. Nothing to prove with facts, just the feel i get. As you get lower in the first the players get less risky, but are still guys who are good football players. In my mind an example is Clayton for tampa Bay. I don't have intimate knowledge of thier draft board, but he was the last WR left in the early first round run. Nothing left to do but take the best one left. Decision easier than Jacksonville who went for Reggie williams the physical marvel with the highest upside, but missed on Lee Evans and Clayton who are better football players.