The biggest problem of GoT towards the end was the lack of any source material and it wasn't something that had any solution so D&D can't be really blamed. However, writers of Witcher do have the finished saga in their hands and they choose to ignore it. While the first season roughly corresponded with the WItcher short stories (much appreciated, no one has ever got that right), the second season is basically going its own way and it sucks. So, 9/10 for S1, 1/10 for S2 - that's 5/10 in average but it will go down with every new season.