Originally Posted by
SirCowdog
The following guide assumes you have both WoD and Legion flying, as well as heirloom gear for bonus experience. If you don't have them your speed will be significantly impacted and you may have to clear additional zones or grind additional trash runs. Conversely, having enchants, food, flasks, and heirloom flight paths can speed up your runs significantly over the long term.
20-58:
ALLIANCE: Loch Modan, Westfall, Redridge, Darkshore, and Bloodmyst Isle
HORDE: Azshara, Ghostlands, Silverpine, Hillsbrad, Dustwallow Marsh
BOTH: Shared zones such as WPL, STV, Blasted Lands, Searing Gorge, etc, are potentially very good, but often suffer from overpopulation. I would only go here during off hours, or if you need a little extra to push you to 60.
NOTE1: It appears that as of the recent buff to random queue exp, it's actually VERY worthwhile to do random dungeons while questing. I would still bail on longer dungeons like Diremaul, Wailing Caverns, and Uldaman. But that may just be my own personal preference.
NOTE2: Get an addon to track rare mobs! Each rare kill is worth ~50% of a normal quest turn-in during the 1-60 range, and makes tagging these guys along the way a very good bonus. Be aware that world scaling does weird things, and some rares may be super-difficult/
58-73:
Northrend quests while queuing for Utgarde Keep, Ramparts, and Blood Furnace. TBC quests, despite seeming nostalgic, are literally twice as slow as Northrend.
Alternatively, stay in "Vanilla" zones until 62. Flying and outleveling enemies will speed up your questing significantly, and more than offset the penalty for outleveling the content. This is especially good for people who despise TBC/Northrend.
74-81:
Set your dungeon difficulty to heroic and proceed to solo every TBC dungeon. Alternatively, Karazhan trash clears(Kill all beast boss, Morose, Maiden trash, exit, reset. DO NOT KILL ANY BOSSES) serve the same purpose.
NOTE: Some people are saying it's possible to start kara trash as early as level 70. YMMV depending on class, spec, enchants, and such. If you can manage it, I'd recommend it. That trash is crazy exp/h.
81-82:
You could potentially continue doing Kara trash clears til 82, but you might be better off doing Serpentshrine trash clears instead.
82-84:
Set dungeon difficulty back to normal and solo ramparts. Some classes can start at 82, others at 83. YMMV
83-87:
Back to questing/queuing for dungeons. Pick Cata or MoP, whichever you're most familiar with. Speed will rely greatly on how focused you are. MoP has the advantage of treasures which can be grabbed along the way for a little boost. Personally I'd stick with questing, since the speed is based entirely on you, whereas a group is random, and you could suffer a lot of wasted time if you get a bad group.
88-90:
Heroic Zul'Gurub. You can clear all the trash(and I do mean ALL the trash, including the fish and gators in the water) for a LOT of experience. Kill the sub-bosses, but do not kill any main bosses. Again, you might struggle a bit right at 88. A lot depends on familiarity and persistence.
90-98:
Use the Timeless Isle portal to Gorgrond to skip the WoD intro scenario. Fly to your garrison and do the quests to set it up(if you don't have WoD flight your speed leveling ends here. Slog through the Dark Portal scenario). Buy exp pots and start doing bonus objectives and treasures. Potentially buy a 630 weapon from the AH if it's available and not too expensive. This will be more powerful than your heirlooms. At level 96 go to Spires and set up the Inn for another 20% experience.
Note: Some people have expressed difficulty with WoD right at level 90 due to scaling and heirlooms not leveling up correctly. If this is a problem, grab some free gear from Timeless Isle, or simply wait to start WoD until 91.
98-102:
Go get your artifact weapon. Some classes will have an easier time passing the required quests. Go back to WoD and continue clearing treasures and bonus objectives on EZ mode because your weapon is OP.
100-110:
Quest, queue for dungeons. Again, go to whatever zone you're most familiar with. Flying will help immensely. Invasions are technically the fastest, if you can do them.
This has all been tested pretty extensively by many people. There are ways to cheese the leveling process using something called "Method zero", but it's questionable whether or not it's against the ToS. Google it and do it at your own risk, and I expect Blizzard to nerf it somehow soon.
For those who are wondering, despite the nerf to exp from having a high-level character in the group, Method-0 is still very good exp/h. At around level 20 you'll be getting ~30% of a level per run of Stockades/Ragefire. This drops each level until around 58 when you'll only be getting ~14% of a level. The same thing happens in Ramparts, starting at ~25% of a level per run, and dropping to ~15% by level 80. I have not tested Method-0 past that, since it seems faster to just play normally at that point.