This episode definitely has its moments.  It's full of neat ideas for the Daleks and feels sufficiently zeroed in on the Doctor and Davros' characters for a return to Skaro.  The Missy stuff might not work with everyone, but I found her very fun and enjoyed the stuff with her, UNIT, and Clara at the top chunk of this episode.  It all felt very true to this world - that UNIT would be keeping track of important Doctor-adjacent people for scenarios like these, and that Missy would be able to easily manipulate the situation to her liking.  I don't know if all the ideas of Davros' past and the Doctor's relationship to him were really paid off in this or the next episode, but it's entertaining and memorable enough this story works a lot more than it doesn't, in my opinion.  It's certainly pretty memorable.