Two problems that need to be addressed before success will come:
1) Team speed.
2) The ability to pressure the QB without blitzing. Continuing to allow the opponent to complete passes at a 70% clip just ain't gonna work...
I would add:
3) The ability to not only hit, but make a tackle. No one on our defense was able to lay the smack down this year. A lot of running and tugging but not much for wrapping up...unfortunately I don't see this changing next year with the inexperienced players that will be stepping on the field.