I'm specifically referring to the way the doctor kills the goblins. If the job could be done with a laser gun then it's not an interesting solution. It would have been better if the Doctor played by whatever magic rules the goblins live by and turn it back on them, maybe tricking them in some way. That would have made the episode end like an actual fairy tale, if they're going to bring fairy tale monsters in they can actually use that to their full potential instead of just "blow them up".