To the best of my knowledge there is no indication in Megillas Esther or in the Talmud that Mordechai conferred with any of the sages at any point during the events leading up to the undoing of Haman.
I would like to know if there is any indication by any commentator that Mordechai did in fact seek counsel, and if not, to know why he was making decisions which would affect the entire Jewish people without consulting with the Sanhedrin, a prophet, or anyone else.