cybed, two issues I can see after a quick look:
1) lack of depth. 4 LBs and 6DBs leave you open to teams wearing you down in the 2nd half.
2) defensive sets. You are running the nickel against the I for sure, and getting pummled on the ground that way. To make matters worse, you are wearing out your DB's that much faster, so when your opponent DOES p***, he's doing it vs. tired DB's.
Feel free to sitemail me with further questions.