It's an improvement, but the weakest NAD starts our 5 or 6 lower than the best, so it will now be 8 or 9 lower. That's still flawed.
Let's keep in mind that epic characters do have more abilities to handle damage, effects, and the like. It might not be a problem that a fighter is hit on its will save more easily at epic than it does heroic, as long as its not on a 2 all the time.