This play it safe, don't force anything, win it in the 4th quarter stuff is just not working consistently enough. If you have a small margin for error and play to be close - the end of the game becomes like a coin flip and then you're talking about 50/50 success rate or worst.
What would it be like if the offense came out in hurry up / no huddle and really pushed the ball down the field? Live with some mistakes early on (when you have time to come back from them). This defense would function better with a 10-14 point lead instead of always playing even or from behind.