I think the examination of the source material, in the context of the TV series, is misleading.
As a product, GoT stands and falls on the piece as viewed by the non-reader of the books (i.e. people like me and the many fans of the series who haven't picked up GRRM's opus).
Source material is just that: source material, it's like good beef stock used as the base for a stew. The writer on a movie set is a curious irrelevance, I've heard it a million times. In this case GRRM was involved, and he happily seemed to understand the compromises and reality behind turning a successful, dense novel into an accessible, entertaining screenplay.
Cheers
MC