Well he was a little too out of it for FOX's Mon-Fri program schedule. I also think it maybe was for health reasons. I know Beck had mentioned a while back he may lose his eyesight. The articles do state he will do some side work for FOX.
Hart's actually made sense, and were often interchangeable as far as order is concerned. I never really got bored of Bret's routine the way I have with the others that you mention. You forgot Cena's though, he's developing quite the formula as well.