Honestly, I feel like GRRM was basically stalling a lot of storylines until he could finish the war of the 5 kings, so there was a constant new diversion in Arya's wanderings. Same with Dany, whose storyline I quite like but still, oh she left one city, oh look here's another city she has to liberate... oh yeah, and another! It's all (interesting) diversion to kill time.
Oh totally. Between the decision to not have a time jump and the decision for this to not be a trilogy of books, there's more filler-ish material as the series has gone on.
I really like Samwell, but it's hard for me to remember him doing anything particularly interesting in A Feast For Crows
- he went to Braavos and then Oldtown so he could be in a position to do something interesting in a later
book, wasn't that basically it?
Daenerys' plot in book two is particularly underwhelming, compared to the strong arc she had in the first book. And it's true that Daenerys' plot, more than anyone else's, has been building inexorably towards a specific goal, which can be pretty frustrating.