What do you mean "major changes"? There are 2 new maps, a new game mode, tons of balance adjustments. The maps are mostly the same. The pre-game interface has changed. There's also now a solid progression system.
I disagree that most maps are poorly designed, but I do agree they could be altered a bit. So many have hallways or paths that seem like they're leading you to a flank point, only to run into a wall that could/should easily be punched out.