This has been something of a let down this season of Game of Thrones. There has been some great moments but largely the episodes have plodded on.
Arya’s storyline in "No One" is pretty well proof positive of that. It deflates like a punctured balloon, setting up a big confrontation between Arya and the Waif, then completely failing to follow through.
— Game of Thrones' bungled Arya plot explains why George R.R. Martin’s taking so long to finish the books by Todd VanDerWerff for Vox