I saw a snippet of an episode in which Taub left because “he wanted to work with House,” which is obviously bullshit. And I also saw, in a different snippet of that same episode, that Foreman fired Hadley because apparently having a supportive girlfriend is too hard on his self-loathing. (And I expect he was genuinely surprised that she immediately dumped him, as that would be in keeping with the general idiocy of the characters, but I was unable to continue watching as I am insufficiently masochistic.)
But why did Chase and Cameron return to the team? Did they lose a bet with God or something?