I don't really think Clara was "re-written" in Series 8. I think she had basically no characterization in Series 7, and she was actually given some in Series 8.
Having said that, I never disliked Clara in S7. But the way her character was rounded out in S8 has made her one of my favorite new-Who companions (behind only Wilfred and Rory).
And Anchorhead, whatever you think of Clara's S8 characterization, there are some fantastic episodes in S8. If you just want to get to the meat of the S8 story, here's what you need to see:
- 801 Deep Breath
- 802 Into the Dalek
- 804 Listen
- 806 The Caretaker
- 807 Kill the Moon
- 808 Mummy on the Orient Express
- 809 Flatline
- 811 Dark Water
- 812 Death in Heaven
- Last Christmas
I will admit that Kill the Moon isn't exactly a highlight of the season (nor is Into the Dalek), but it contains important character development/story arc advancement. Flatline is less central to the story/character arcs, but it's perhaps the best episode of S8, so DEFINITELY watch it.
I skipped 810 In the Forest of the Night because, while it contains something that could be considered important Danny/Clara arc advancement, it's not brought up much in the episodes that follow, and Forest is widely considered to be a poor episode.