The structure is very similar to the Wire in that it asks the viewer to follow and track the characters over time and so long as you have a reasonable ability to hold material in your head you shouldn't struggle to follow it.
Except if you look at The Wire on a single-episode basis each installment did have its own story with a beginning, middle and end, within a season that had its own beginning, middle and end. Game of Thrones had a couple episodes this year that were purely about moving the pieces around (episode 8 was one for sure, and really dragged as a result) and the season as a whole really felt like Part 1 of 2 in a way that last year didn't.
Now that they're scattered it makes perfect sense and I think drawing in the focus even more would remove much of the shows strength.
You don't think Blackwater was the best episode of the season? I thought it was, by a wide margin, because
it was so tightly focused.
Well yes Blackwater was the best episode and part of that was
the tight focus BUT it was also because it managed to plumb some of the strongest emotional depths of the show through what was going on.
I disagree with your characterization of Wire episodes. I think the episodes only have a beginning middle and end if you force such a structure onto them. Simon himself has said that while the Seasons do the episodes emphatically do not and are not intended to. There is definitely a tighter traditional story telling with each individual season for the Wire (something that makes a great deal of sense given each season has a different focus).
And I didn't think Episode 8 was just about moving set pieces at all (a criticism that could be somewhat fairly leveled at Episode 7). The scenes with Robb alone in 8 disprove that because those were crucial to his character development. Don't think the scenes with Tyrion stand to that criticism either. The only scenes I can think of that really do that are the ones with Dany.