The overall "arc" are this season resembles the first Doctor’s time. PC’s first story is somewhat prehistoric. The next installment is a Dalek tale. Then a “historical” themed episode. I am unsure of the next episodes but the season culminates in a Cyberman adventure. I know this is only a passing similarity but I find it intriguing nonetheless.
The historical stories in the original series didn't really incorporate any sci-fi stuff apart from the Doctor, his companions and the TARDIS. The last of these type of historicals came out during the Troughton era, although Black Orchid from Davison's first season sort of counts. (Although the audios and novels have also featured historicals) The stories set in the past in this season that we know of involve robots and probably more sci-fi stuff as well.
Big spoilers below. Click at your own risk. Spoiler: Full season run down 1. Clara trying to cope with her best friend being someone else. A terrifying monster. 2. Gritty Dalek episode that goes into the last place in the universe the Doctor should be. 3. Very funny Robin Hood story all about being a hero and whether the Doctor is a good man. 4. The story of a date and the Doctor having what appears to be a mild nervous breakdown. Tiny guest cast, no CGI. A bit of Coupling. Quite scary. 5. A Doctor Who heist movie with a cracking monster, one of Neill Gorton’s best. 6. What effect would slipping away with the Doctor have on your life? A hoot with some serious bits. Bit like ‘The Lodger’. 7. Proper drama with monsters and all the Doctor Who stuff that you could want. Also features a callback to a past episode (sort of). 8. Moffat playing the long game with a callback to something from Matt’s first series. A brilliant idea of a monster. Foxes singing. 9. A horror story that starts off with a very cute idea and becomes really quite frightening by the end. One of the best ever sight gags in it. 10. Boldly beautiful, lyrical and poetic. A fairytale, but not Moffat fairytale. Quite different with a clever main visual idea 11/12. High octane action, with Cybermen and some proper UNIT stuff. Strong emotional story about Clara and the Doctor and the fact that the way they interact might not be healthy for everyone around them. If there's an arc it'll be one that accumilates in the final two episodes, unlike one that unfolds throughout the season. Or one that should be mentioned. Like finding Gallifrey...
Hopefully the season ends with the long slow death of Clara. I would be happy with instant death so long as she is gone for good.
Spoiler: Spoilers in first episode Not in the slightest beyond the appearance of prehistoric creature in a different time period.