Brienne's dilemma in retrospect?

Well depending on how they play out the Riverlands stuff which we know we're getting in some capacity this season just based on the trailers (not going to list any spoilers) I'd have to say it looks like Brienne's story still has a long way to go.

She has had a rough journey thus far, failing as many times as she has starting way back with Renly so I'm personally glad she's finally getting something good alongside Sansa who has also suffered enough.

But I do agree she's had no real 'oathbreaker' moment other than failing by circumstances to get Sansa and Arya the first time around. She did try.

But it was clear that she abandoned her watch for personal reasons.

Or, at the very least, that her oath to Renly conflicted with her oath to Cat in that precise moment in time. She had to choose and she chose to go after Stannis, leaving Sansa to fend for herself (which she did).

I definitely think the audience has had enough of Brienne trekking across Westeros chasing after Sansa and Arya and staring at Winterfell so they really had to do something with her after putting her on the back burner for so long. Due to switching around the storyline (Riverlands delayed) both she and Jaime needed something to do and stalled a bit. 

Unless Brienne runs into LSH who somehow knows Brienne abandoned her post and gets pissed off this is another example of sloppy writing. Brienne gets to do both things she wanted to. Sansa was in danger for like 5 minutes, if Sansa died or something there would be consequences here there aren't any.

I loved the scene and Sansa, Stannis and Brienne s5 stoylines were disasters so I'm not surprised by this development At least the scene was well done.

I assumed that abandoning her post would mean that Brienne lost her chance to find Sansa, and thus I was surprised when Brienne came to the rescue. I assumed that somebody would rescue Sansa, but I thought it would be random Northern loyalists, not Brienne. So that was an exciting moment to watch. And Brienne's victories are so badly outnumbered by her defeats that I was glad she got to find Sansa.

Also, death by Brienne wasn't a terrible end for Stannis.  He died to a respectable warrior for a just reason, in a clean blow. Better than being picked off by Ramsay's men or somehow surviving and escaping to linger on in misery and irrelevance.  In retrospect, I think Brienne killing Stannis was more about giving Stannis a proper end than it was about influencing Brienne's future.