Who doesn't like a good story about witchcraft? Sort of difficult to mix it up with SciFi, and this episode was an example of what doesn't work when combining the two. An example of doing it right? An episode called Catspaw from the original Star Trek series.
This outing with the Doctor was disjointed, senseless, unimaginative and boring. Found myself zoning out on much of it, which is what whoever wrote it must've done while developing the story.
Can't count it against the new Companion or the Doctor though, I still think they're well cast for the roles -- this was just a terrible story.
In my opinion, they need more episodes along the lines of The Impossible Planet/Satan Pit (2-parter from season 2) a high point for the series. This definitely wasn't it.