I think the reality is, they just decided they didn't want actually go through with her character arc. They didn't want to actually have Arya have the ability to change her face, since they'd have to pay another actress(s) to essentially play Arya, playing other people.

They messed with the pacing and thought Arya going blind would be a good way to end last season, instead of let's say during an episode 8. So they then essentially stalled, then attempted to play out 1 chapter from TWOW that they weren't willing to pay off.. thus meaning she's essentially spent 2 seasons in Bravos for nothing.

It's been a shaggy dog tale, the same with Jamie. They followed the books first few seasons, then around season 4 they decided to get cute... and have managed to turn a character who starts of as a villains, embarks on a redemption arc back into a villain again for no reason, other than bad writing. Jamie abandoning Cerseri, burning the letter... all gone. It's a worse change than having Jamie randomly rape Cerseri in season 4.

Arya jumping from the roofs like an assassins creed character despite being stabbed the previous episode is one thing, but Brieene and Jamie having a conversation about the Tully army joining the Starks in a rebellion against the fucking Lannisters is beyond absurd. Jamie while trying to end the Tully's rebellion, would just let the Tullys leave then join up with their enemies in the North?

Also the amount of stalling this season. Tyrion only appears on screen, because they have him under contract. They should not have burned through his ADWD arc in 1 season, if they were just going to have season 6 end with a siege anyway. Varys is the same, but in his case he's a major villain who should be

this season, instead he'll probably just pop up in Dorne. King's Landing is the same, they burned through most of the story in 1 season while skipping over important sections.. just to get Cersei naked, unfortunately they didn't know what to do next. So 9 episodes of stalling, then they'll kill off a bunch of secondary characters in the final and pretend the plot has advanced.

No matter what happens in the next episode, just remember that it's likely Stannis (not Jon) in the books.