??? and?? The murder Eddard Stark developed Arya. What's the issue with the rape of Sana developing Theon?
The execution of Ed Stark was a shocking but fitting end to his character arc and set the tone for the entire series. It established The Game as we know it. That death had an effect on EVERYONE'S character development, and made narrative sense. It is literally the polar opposite of Sansa's rape.
Also, it ended Ed's character on the show, so it's not like he went on to continue being tortured day in/day out like Sansa.
Is any particular violent scene needed? I could list out a dozen things the show has dealt with and come up with a possible alternative. I don't think that's a good argument against it. Also, having characters act because someone else is done wrong is not 'problematic'. Why do you think it is? Virtually every time it's used you're supposed to be incensed that it happened...it is in no way legitimizing or encouraging or making light of the rape. Do you feel that same way about having a character murdered in order to change a different character? If not, then why?
It's problematic when it becomes an incredibly overused way to increase the stakes for female characters and/or "make them stronger."
Again, a lot of people who have a problem with that scene aren't upset merely the rape, but what it means for Sansa's development, and what it says about the writers, that THIS is what they keep coming back to.