Early in the show Sansa and Arya are reflections of each other. Sansa is a romantic and falls for a monster. He and his family then tortures her for years. She gets out with another kind of monster, Littlefinger. Littlefinger appears to have a crush on her and it looks like she learns from his cunning ways. She goes Goth-Sansa and looks like she's out for revenge. Then she get's captured and raped and tortured some more. And it's like great, another classic GOT trick. Except it starts to wear out it's welcome. It feels predictable. And oh the audience is mad that the writers showed rape? Better make the plot contort in the next season so that Sansa gets revenge. I don't know. It's not terrible storytelling on it's own. But in the context of what the show has already done and the patterns it's established it felt very predictable and poorly executed. But that's just my feelings on a show that I think started as a really great adaptation and has kind of veered into a weak adaptation.

Regarding rape as a plot device. The idea that the point of view should be of the rape victim and show their pain is important in that it is rare. But I think you bring up an important point that Reek was a victim of this man too and that complicates it. But we've been given Reek scenes to show his suffering and get inside his head. Reek witnessed Sansa's rape. It was a poor choice of POV because it is the common choice.