I play on 360... as Arkansas (B+ rated defense) in dynasty...
I've played about 6 games vs. CPU, five of them on Varsity and one on All-American. AA was so hard I thought I was playing on Heisman. I've always played AA from the get-go on previous versions, but not on 08.
That said, I haven't stopped anyone I've played. The ONLY way I've stopped 'em is by interception or fumble and that is nothing I did -- it was my CPU controlled player making the pick or gathering the fumble. In six games I've probably forced MAYBE 6 punts.
Mostly teams are passing like a hot knife through butter... I try to match their receivers -- if they go 3 wide, I counter with nickle or dime, 4 or 5 wide and I go with dime. I tried using a lot of zone, which worked too well on 07, but the QBs picked it apart. Now I start with 2 deep man and mix in zone blitzes.
My last game Kentucky was running a lot out of 3 and 4 wide sets and was chipping off 7-10 yards per run. I went to the 4-3 and played lots of zone blitzes. I only got one sack and I only gave up 14 points, but they moved at will and I felt helpless and bored.