Emperoreddy
Show Me What You Got!
They were pretty much stuck with a plot line that was never going to contribute heavily to the end game, but felt they had to include it because the books deal with Dorne. It was terrible and could have been handled much better, but I don't think it was ever going to feel satisfying and be any more than a side plot.
You could kind of feel the whole show slowing to a crawl as it came up to the end of Dance with Dragons. Like they both were trying to give George one more year to get something out, and that they weren’t 100% sure where the subplots were even going.
Once through that barrier the show seemed to hit hyperdrive as it starting cutting down subplots and speeding towards the end.
It always felt clear to me that they never actually thought they would totally catch up and pass the books until about a year or so before it happened.