I'm trying the 0 rush D for the user right now and it seems like there is almost no difference than when I had it at 40. I'm not using that whole set tho. I'm using these:

Game Play Sliders: User/CPU
QB Accuracy: 10/5
Pass Blocking: 40/40
WR Catching: 35/35
RB Ability: 55/75
Run Blocking: 0/50
Pass Coverage: 65/75
Interception: 45/45
Rush Defense: 40/55
Tackling: 50/50