In order of importance to me personally:
1) Make high discipline prevent penalties more.
2) Make high avoid fumble prevent fumbles more.
3) Better QB reads combined with better DB play - passing seems pretty balanced power-wise right now, but too dependent on WR making crazy catches and not enough on the QB hitting the open WR.
4) More defensive play variety, probably by making zone plays better. Fixing #3 might make this better too, because if you have better DB play, you may not have to depend on the trifecta of intense pressure, elite skill levels, and lucky to stop the pass.