First things first. Paul Heyman wrote 200+ new universe storylines, plus helped with the attitude era mode.
"Gamers will now not only be able to control what types of stories can play a role in their simulation - turning off injuries or narratives that break up tag teams - but program their shows for any day of the week, or delete shows entirely. Each recurring show can have its own superstar roster, belts, arenas, match-up screens and more adjusted. There’s less emphasis on conforming to what the WWE does now, and more thought towards allowing gamers to do anything they would want. But if a player’s modifications eventually get a bit cumbersome or confusing, Universe Mode now has the option of being completely reset."
They've also added detailed statistics to universe mode, tracking of title holders, and historical statistics and such.
Now another thing about the online, they've added a "fair fight" option which makes everybodies stats the same in the online match.