Offenses have figured out Pellini's attack style of defense. Its almost useless to blitz if the QB rolls out or takes a three step drop and throws, i.e, getting rid of the ball quickly. Teams are also swinging backs of the backfield to help slow down the pressure from blitzing. Teams normally don't blitz as much if the "cost" of attempting it is too high.
I liked that they blitzed more this game then any other that I can remember. The D played big tonight I thought too.
If you look at the scoreboard and judge the defense based off of that, it is misleading. Keep in mind that 2 of Bama's td's were the result of a very short field due to turnovers. Another one of their td's was on a punt return. So 21 points were given up due to poor offense and poor special teams.