At this point the show is deviating so much from the books it might as well be another story. Can't entirely blame the show runners, if anything it's indicative of the declining quality of the plot past the 3rd book. The show cleaved rather closely to the book plot up until this part because it was a tighter, more closely connected story that worked almost flawlessly, not the meandering, separated parallel plots that followed. Martin has been struggling to tie up all these free floating loose ends for the past two books, what he calls the "Mereenese Knot". It looks like the tv show will get there before he does, and it will be only loosely if at all connected to where the books will end up.