No need to part ways with Brady he is still good, and the only question is health. If the Pats can be healthy on both sides of the ball resign Edelman and Talib they will be a very good team. The defense even with all the injuries took a step forward. They just need a piece or two. If they can get another guy opposite of Jones and possibly another good linebacker in the draft they would be set. The defense will be very good next season if healthy, and if Talib resigns. Have high hopes for both receivers. Although I don't think either of them will be number one receivers I think they both have a chance to be really solid. Love Dobsons game so far. The big question is Gronk and if he can remain healthy through 16 games. I'm not sure a guy like that can stay healthy given how he plays the game. Pats could get away with not having a legit number one receiver if Gronk is healthy, and they have solid options. I have high hopes for the defense next season, and especially Collins. If he can do what he did the last few games all season long that would be huge for the Pats.
As for your other question. It has mostly been Brady. Although, I need to see a breakdown of this game. In the last few games Brady has been reluctant to throw the ball and then starts seeing ghosts in the pocket. He wasn't jumpy in this game, but he didn't look great. It also doesn't help that his skill is diminishing. Also, Brady's decision making takes a nose dive in the playoffs. Take a look at that Slater deep bomb. He had forever to throw, and decides to throw it to a well covered special teams player. The defenses are better in the playoffs, and for the most part the refs let things go. You have to make better throws into tighter coverages, and at times Brady seems reluctant to throw into those spots except when he has a receiver like Gronk. Even when he has someone like Gronk though he makes dumb ass mistakes as well. Will force feed him the ball and forget about everyone else. I'm no football expert but this is just what I see.