Sorry, to make it clearer, since I think this may actually be a temporary fix for xbone users.
Whilst on the connecting to online screen (if it is taking a long time) return to the dash board, press start and quit the game. Then reload the game, connecting to online should now work faster for a limited amount of time, if it does work faster, then you lose less time doing it this way.
With this in mind I'm guessing this issue is to do with user profile and possibly the kombat pack update, just a theory though.