I don't need to play it on the Wii U to tell you that it wouldn't work any better. I'm pretty sure the game's code is the primary issue. It has to have slow down because desyncing would be worse.
And even if it were somehow the Wii's Internet speed, the game is still going to be as fast as the slowest connection. So everyone would need to be using a Wii U for this to even have a chance of working. --- http://i.imgur.com/rbBq9.jpg Come to the board in my quote for math discussion and pretty much anything else.
I wanna see a video of Brawl running on a Wii U that's connected with an HDMI cable to a HDTV. --- "When I tell the truth, it is not for the sake of convincing those who do not know it, but for the sake of defending those that do." - William Blake