I do not think the joker is the one masterminded A day. In The joker war, special joker says he will leave bane alive, and Joker keeps his word he said he was not going to kill bane. then there is the gas used, it did not make you laugh, which is what Punchlines version of the gas does not cause laughter. Also there Simon Saint working with Scarecrow who was supposed to be in Arkham.
I think the joker was framed, by eather punchline or Simon Saint.