Brienne's scenes are exactly as she is portrayed in the book... she isn't expressive or animated, she is awkward and wooden... and resolutely determined to ignore any goading she is subjected to, having been subjected to it her whole life for being the only (known) female knightly warrior in the Seven Kingdoms. Yet they portrayed well the seething anger which lies under the surface of her stoic demeanour, when she maliciously (deservedly, but maliciously) gutted the Northman who had put one of the whores who lay with Lannisters to a slow and painful death. I also think she looks the part too, powerful and broad physique with barely even a hint of comeliness about her.