As I hear about the introduction of partial node harvesting in 5.3 I am struck with an idea that reaches to the very core of WoW's design. Perhaps, though grand at first, making wow a bigger and more expansive game with each iterative xpac was a mistake. Or was good at first, but is increasingly resulting in a unwieldy and hollow behemoth loaded with abandoned outadted content.
What if... not just mining and herbalism could be levelled in Pandaria. What if an entire character could be levelled and played entirely in MoP content? What if the WoW formula was tweaked as such that each xpac was the xpac everyone played in?
It's a bold proposition, and I know many of you are adverse to even modest propositions, and will most likely flail in outrage at the idea, but hear me out. I'm not saying you should be able to go back and play BC, WotLK, and Cata content. I'm saying it should be taken out of the current gameplay experience and left as an optional aside. We need to face facts. Outland questing sucks, Northrend was amazing, but is now empty and devoid of activity. The drops are irrelevant, there are dusty halls where you can trade in expired raid tokens for expired raid sets. It's kind of depressing, and irrelevant to current play- yet these fixtures remain. I think it's time to call a spade a spade and designate this stuff as retire content. If you want to go back and play through this stuff, I sure think you should be able to; get xmog sets, old mounts, titles, achievements- but levelling through this content shouldn't be mandatory or even intended.
Obviously, there are huge questions. How can one level entirely in Pandaria? It's possible through clever overlapping of content- such as with allowing people with a mining skill of 1 mine the same nodes as someone with a skill of 600- just with a different payoff. What about enemies? It's a bit too much of an ask on devs to remake 1-85 content just for MoP- then do it again andf again for each xpac. What about 'levelling zones'. We have the wandering isle staring experience. It gets you up to level 10 or so. We have Pandaria which has content for 85-90.
What if the Jade Forest, The Valley of Four Winds, and the Karasang Wilds were designated 'levelling Zones'. In these zones you have players from level 10-89 all levelling. The content is the same, but the enemies are modular. Instead of having fixed levels, they have relative 'difficulties'- if you pull one it is assigned a level and stats based on your level. Enemies in the Jade Forest are easy, the Valley of Four Winds is full of medium enemies, and the Karasang wilds is full of Hard enemies (with some exceptions for all zones).
This way you recapture that vanilla feeling of a world full of players levelling just like you. You'll be running around sharing the zone with players 20 levels your senior and junior. PvP servers will be brutal, one part of me wants to suggest phasing these three zones in 20 level brackets to mitigate that, the other part of me relishes the idea of pretty much every levelling player on a PvP server as various sized fishies in a rather small pond.
This is just an example hypothetical. Come to think of it, questing is very much the 'levelling' gameplay style. You don't really do it at end level play all too much. The world is for questing. Thinking of it that way, why not make all of Pandaria in this overlapped modular way, where levelling players of all levels share this content. Once you hit 90 you're king of the world, but no longer really need to quest in it, and more inclined to do things like instanced PvE and PVP.
A more advanced formula along the same kind of lines is to have a conceptual range that slowly climbs as you level. So at level 11 Jade Forest is set at the 'challenging difficulty' and the Valley of Four Winds is 'very Hard', whilst Karasing Wilds is nearly impossibly hard. By the time you're at level 50, Jade wilds is now easy (enemies are set to be roughly 10 levels lower than you), Karasang Wilds is medium (enemies set at about your level when you pull them), whereas the Vale of Eternal blossoms is still really hard (with enemies 10 levels higher than you).
TL;DR: What if the forumal of WoW was tweaked to incorporate fuzzy levelling and modular challenges so that current xpac content is shared by all players- with old xpacs being shelved-but-accessible optional content and not an essential or encouraged part of the levelling process. The goal being to make each xpac play and feel a lot like the World did back in Vanilla; rather than the game getting bigger and emptier.