When World of Warcraft: Shadowlands arrives — or, most likely, when the 9.0 pre-patch arrives — the leveling scheme for the game is going to be turned upside-down. There will be a huge level squish and players will only need to select one expansion (including the vanilla content) to go through before reaching Shadowlands. Not really sure how this will work AFTER Shadowlands, but Blizzard never thinks that far ahead.
So if and when I strike up alts to go through this new leveling regime, I’m going to have to choose. We all will. And so I’ve made a ranked list of the expansions I’d elect to go through, starting with the ones I would rather not and progressing to my preferred picks.
Bottom of the list: Cataclysm
I wasn’t really present for Cataclysm but have never gotten the impression that its scattered zone experience would make for really juicy leveling. I mean, it IS more modern than, say, Burning Crusade, but that’s all I can think of in favor of it. Speaking of…
The Burning Crusade
There are a couple of great zones in TBC that I hold fond nostalgic memories, but the whole expansion is very old and creaky at this point and hasn’t received a revamp. It’s just not something I want to re-experience, especially with so many better options on the table.
Vanilla
Vanilla zones would hold some measure of nostalgic fun and be grounded in your base World of Warcraft experience. I did enjoy revisiting these in Classic, and probably wouldn’t kick and scream too much for the 9.0 version. I don’t think I’ve be leaping at this either.
Mists of Pandaria
One big pro of this selection is that I’ve simply never done it. Well, not all of it. It’s virgin territory for me. One big con is that I’m not that keen on the heavy Chinese theming, which is why I’ve never done it. It’s a more viable option for maybe one trip through at some point.
Warlords of Draenor
Shedding the baggage from the expansion’s past, as a pure leveling experience, this was pretty good. Attractive zones, interesting stories, and more modern map touches (including treasures). I’m not going to rank it higher because I’m going through that right now and probably won’t want to do the whole garrison building thing again so soon.
Wrath of the Lich King
Everyone’s favorite (or so the crowd would make you think). I adore the zone biomes and the whole theme of the expansion, but like TBC, it’s getting older than you might realize. It would be very interesting to experience in its entirety once more, however.
Battle for Azeroth
BFA gets a whole lotta crap these days, but I really, really enjoyed the questing and leveling through the Alliance zones. They all look amazing and the seafaring focus gives it this neat nautical tinge that lifts my spirits. I wouldn’t object at all to doing this more in the future.
Top of the list: Legion
But I have to give Legion the top ranking here. It was a terrific expansion with lots to do, and just about every zone is wonderful. Dalaran was a great core city, there are lots of treasures to find, plenty of cosmetics and pets to collect, order halls to build, and so on. Legion is the best of the “modern” WoW expansions, and it would be at the top of my preferences for at least one of my characters.
Bio Break 
I understand why Cataclsym is always in the bottom of many people’s lists, still i think each cata zone is worth trying at least once, they are dense with quests so no need to travel between them, also they are connected with portals in the main city so they provide quick travel.
Vashj’ir is the zone many people hate for a good reason, it’s huge and takes a long time to finish, and yet i think everyone should finish it once, maybe they’ll hate it and never come back, or they’ll love it and never come back! because it’s overwhelming, but it’s a beautiful place.
I’d probably put Warlords of Draenor bottom because, well, up to now it’s been the bottleneck that every alt has to go through. Yoiu can do either Outland or Northrend at 60 (and Northrend has two different starting zones, at that), and free choice of Pandaria or a Cataclysm zone or two from 80 onwards, but as soon as you hit 90 you MUST trudge through the “Welcome to Draenor” tour of the Tanaan Jungle with Khadgar and co.
Probably partly my fault for wanting to get all the Legion class mounts and allied race heritage armour sets, but I’ve now gone to Draenor so many times that I’m really, really looking forward to NOT going to Draenor on the handful that haven’t made it that far yet.
I stopped chronologically after Warlords of Draenor. People keep saying that Legion (which should be my logical next expansion) is amazing and thus I keep feeling lured into it once again.
I wonder if it would be a bad idea to wait with that until after the level squish?
My top priorities would be 1) Mists of Pandaria, 2) Wrath and 3) Outland. All have felt almost meaningless for the longest time despite any scaling tech – the content is too easy and too quickly out-levelled. Giving these a full play through to level 10-50 will hopefully allow me to enjoy exploring the content at a more reasonable pace.