A full revamp on the scale of Cataclysm isn't necessary. Some zones that focus way too much on Horde vs Alliance could use some rework, as do zones that are suffering from the Cataclysm. Having Alliance and Horde fighting non stop in some zones since Cataclysm is no different to Stormwind Park being on fire for as long as it did. If they decide to go for a full revamp I sincerely hope they go with more of an adventure-style rather than a hero-style. It's just retarded how many times you figuratively save the world as you level-up. The human starting area (talking about just the abbey) even has you thwarting the Blackrock orcs before you can even select a specialization.
What's more important to me than story cohesion is the overall questing experience. Currently that's very lackluster until you reach MoP/WoD. There are still zones where you spend more time traveling to/from a quest hub and between mobs you need for a quest. It's still way too easy to outlevel a zone. It's still way too punishing to switch your leveling route (say going from EK to Kalimdor). If you pick up a Call to Arms quest in a city, you should get a complimentary flightpath/portal. Flightpaths to the major hubs that start a zone's questline should auto unlock once you reach that zone's minimum level requirement. To combat the outleveling issue even more they should implement level scaling to some extent.