^I think your reasoning is somewhat unfounded when it comes to Arya. We know very little about how this whole "no one" thing works. She obviously hasn't passed the test – otherwise they wouldn't have sent her to kill the actress. Perhaps not being affected by the water was a sign that she was making progress. But anyway, we don't know very much about how the water works either... maybe it's not that simple. Same with Benjen – let's not pretend that we know everything.