I think the frustration stems more from the idea that they took a player that wasnt a huge position of need. When you do that, you typically expect the player to show something and be worth at least where the Cards picked him, hence the BPA idea.
Although i agree with most that it is rediculous to judge 4 games in, but there were reports early on that he wasnt trying and BA called him out, that is obviously not a good sign.
Could have taken someone to shore up the LBers, Cards wont be able to pay all these linemen long-term anyways.