I don't like Moffat's character arcs. I really wanted Clara to be a normal companion, but instead we got another overly complicated back story.
That's the role companions play nowadays. They need something to do. They need to be a part of the season in some way.
Otherwise people would complain that the companions are just set pieces. They're just there. They don't contribute to the overall story.
They are supposed to be there as a contrast to the Doctor and the face of the audience. To bring the human side to the Tardis' journey, someone the audience can relate to when the shit hits the fan.
Adding mystery to the companion distracts from the story. I wish it would end. Hopefully 12's tenure will keep it that way now that Clara's backstory is revealed.