there's a few ex DW cast members in Broadchurch...all of them victims of the Moffat era..
I think it's a case of PC box ticking by the BBC. There has been a concentrated campaign to force this through regardless of whether the show needed it or not and many of the people who wanted it, will see it as victory, move onto the next cause and never watch a single episode.
However, nothing will save the show from the massive shit filled cluster fuck that Moffat has created so when the show finally tanks, who will get the blame...probably the first female doctor.
it's a children's programme man, go out and get a girlfriend