So, XCX is not the Wii U 95+ savior some people here tried to sell us for months. Big deal.
84 is a good score, especially if the game really has the issues told by others in this thread. It will change nothing IMO : it's the only new Wii U release for the end of the year, interested people will buy it, the broad audience won't. A 94 MC wouldn't change that.