Star Trek and Stargate come to mind. Tbh, I think there's merit to both approaches. Sometimes when you have more than one head writer, either they'll end up not getting along or both will end up doing a bad job, and you're no better off. I certainly would say that Moffat and Davies have their faults, but overall I think they've both done admirable jobs.
Oh man, you gotta power through it. IMO S7 is the worst season since S1, but S8 gets a whole lot better.