Reggie is a pricey decoy, that is true. But! it has to be on plays that he CAN be successful else opposing defenses are not gonna take the bait. And that means getting him downfield some, in the short to middle range and having him run crossing patterns to pin the LBs and maybe a DB as well. At that point defenses have a choice, man-up on Bush....good luck with that!....and take a chance he busts a big one, or, do as most do, double-cover him, providing easier targets elsewhere for Brees.
But, having him line up 7 yds deep as a RB is a disaster waiting to happen, as is throwing screens to him. Bush does not follow his blockers and often doesn't even try to run the play the way it has been designed.
Bush can be an effective flanker. That's it.