Do you think the writing is affected by the actors and casting?
Sure, the writers are for the most part following GRRM's books and outline, but how much wiggle-room do they have to give more screen time to characters who click with audiences, or to write out those who don't? This is a particularly big question for child characters, would Arya still be around if Maisie Williams weren't so talented and likeable? Would Bran have a larger role if audiences had more interest in his journey?
I have to say, the casting department has done an excellent job, particularly with the kids who have literally grown up in their roles. Even small parts like Robyn Arryn, that child actor has gone from being a perfect little beastly child to a highly slappable teenager. He's terrific.