I really love the atmosphere of Feast
too. It has obvious structural flaws thanks to the various reconfigurations of the overall story, but as you say there's something mournful and eerie about it, as a moment of potential rebuilding declines into further conflict and magic slowly creeps back into the world. Even Maggy's prophecy, which I know a lot of people don't care for, works for me in that respect.
The Tyrion chapters in Dance
are a problem. There's something to be said for the psychological progression there, but I think Martin got too drawn into the Essos world-building involved, and let it expand an already languorous arc.