They seem to have given up on this idea that every bad guy has to somehow reflect a facet of the Doctor. I can see why - he's an interesting, multi-faceted fellow, but it must have become a bit of a strain over time. Instead, it was Clara who got this weeks 'reflecting the Doctor' job ...in fact, this time around Clara actually got to BE the Doctor.
The switch between the two was nicely engineered, with the old 'trapped in another dimension' angle reworked via an entertainingly shrunken Tardis. I liked this. I hope the toy companies bite. There are several little Tardises scattered around my house, with all sorts of folk lurking around inside: Lil'Billy and Chris here, floppy Matt there - I'd love to have one that opened to reveal a massive Capaldi eye-brow.
Once established, it's a shame that Clara didn't get much to do with her Time Lord role. If this was meant to provide us with another opportunity to ruminate upon the moral nature of the Doctor, they could perhaps have provided her with something more morally ambiguous to do. After all, we know that she's up to the big jobs - she nearly blew up the moon a while back. As it was, all she did was save some nice folk by running around in a tunnel pointing the sonic screwdriver at things - hardly a profound exploration of her mentor's ethical stance. The only philosophically troubling element was that in doing so, she also inadvertently managed to save an unpleasant looking, grumpy old man in a tabard, whom no-one seemed to like very much*......but as Kant** would tell us, it's our treatment of such people that lies at the very heart of moral behaviour. ***
* This was the same fellow who was hung off the side of a building by Michael Keaton's Batman twenty five years ago, so it all probably appeared terribly sophisticated in outlook to him.
**I'm not sure that Kant would have watched Doctor Who - what with the way the BBC keep messing with the start time.
***Sorry, I've written a post with three footnotes and a mention of Kant.....