Well I watched all of season 3 here are my thoughts:
Hugh Bonneville did nothing this season but get more angry then ever, He was just badly written this season. His best tape would be episode 8 (uk episode list)
Michelle Dockery was her usual self except in the first episode where she had a very powerful scene. Episode 1 would be her best tape.
Maggie Smith continues to be the best thing about the show. She should submit an episode opposite Shirley where the two were both great.
Joanne did nothing compared to last season.
Jim was almost as badly written as Robert.
Brendan did get some good material but it was when he was in prison, that was about five minutes an episode.
Elizabeth was great and would be the best nomination after Smith.
Shirley was great in her two episodes. She should be a lock nomination maybe win if the academy still likes Downton.
The season had an ok arc but it's best actor was Jessica playing Sybill especially when
There is still the christmas special.