Yeah exactly - when they started writing plot GoT went off the rails. This bodes well for 3 body - it's right up their alley - huge cast, intrigue, spectacle and surprises that shock at first but make perfect sense in retrospect. I've got hope!
They had already run out of books by season 6 and I'd say it was one of the best if not the best season. Yes it was a bit lighter on the plot than earlier seasons, but the execution was damn near perfect. But from there they stumbled over their own lack of ambition and morale. They could have had two more full seasons from the studio, but decided to cut 7 and 8 down drastically, while already being halfway off to their (ultimately doomed) Star Wars project.