I highly recommend actually staying in the 20-60 range zones until you ding 62. The reason for this is that despite getting a slight penalty in experience for being over-level, the advantage of having flight will more than offset this. That, and WOTLK and TBC zones are the slowest part of the leveling process. Minimizing your time there as much as possible is worthwhile.
Excess Potion of Accelerated Learning: Acquired in your Garrison (part of the Warlords of Draenor expansion), this gives you a 20-percent bonus to experience from killing monsters and finishing quests. It lasts one hour, but you can buy it multiple times and use it back-to-back. Alliance players buy it from Sergeant Crowler, horde players buy it from Sergeant Grimjaw. Does not work above level 99.
But the system offers a painful and mindless grind. At worst, it feels like a cheap and artificial wall blocking you from playing your character to its full potential. Levels of your heart come fast at first, but the costs become prohibitive when you get up into level 20 or so. This wouldn’t be an issue if the most powerful Azerite gear didn’t require reaching level 22 to unlock even 75 percent of their full damage, leaving players left out of features from gear they’ve already collected. This means more grinding.
Set sail for the previously unmapped isles of Azeroth. Battle in groups of three as you race against cunning rival intruders—or enemy players—to collect the island’s resources. Constantly evolving challenges await as you traverse frozen landscapes near Northrend, open the gates of an abandoned Gilnean castle, navigate a war between elementals and more. Tides of Vengeance adds two new Island Expeditions to the mix and two new random events, as well as updated rewards.
Island Expeditions: 3-Player co-op with optional 3v3 gameplay. Players will explore uncharted isles across the Great Sea. There is azerite and other unclaimed resources bubbling to the surface that is highly sought by both factions. Complete varied and dynamic objectives with a large variety of challenges to overcome. Race against advanced AI opponents designed to thwart players using tactical and strategic moves that consistently change. Optionally, players can choose to race against other players, creating a 3v3 PvP environment.
In Kul Tiras, the Alliance's initial attempt to gain the nation's assistance ends disastrously when Katherine Proudmoore, Lord Admiral of Kul Tiras and mother to Archmage Jaina Proudmoore, not only refuses the Alliance's request for aide but also orders Jaina arrested and exiled for her role in the death of her father, Daelin Proudmoore, in the aftermath of the Third War. It quickly becomes apparent that Kul Tiras has become mired in corruption and outside threats, so Anduin and Genn Greymane send Alliance Champions to aid the Kul Tirans and earn their trust. Aiding them in this quest are Flynn Fairwind, a "retired" privateer, and Taelia Fordragon, the idealistic daughter of Bolvar Fordragon, former High Lord of Stormwind and current Lich King of the Undead Scourge. The Alliance is successfully able to earn the trust of Kul Tiras by combating the pirates of the traitorous Ashvane Trading Company in Tirisgrade Sounds, the Naga and corrupted agents of Queen Azshara in Stormsong Valley, and the occult forces of the ancient, ghostly warlord Gorak Tul in Drustvar. After these threats are defeated, Katherine is left despondent at her inability to lead her people, and resolves to help the Alliance find Jaina and reconcile with her. The Alliance eventually track Jaina to the prison island of Fate's End, where Gorak Tul, having survived the events of Drustvar, has kidnapped her and is tormenting her with visions of her past failures. The Alliance champions and Katherine destroy Gorak Tul once and for all and rescue Jaina, who is finally able to let go of the hate, anger and obsession with the past that defined her ever since the destruction of Theramore. The Alliance and Proudmoores then unite to defend the capitol city of Boralus from a massive pirate siege, after which Jaina is named Lord Admiral and pledges Kul Tiras' navy to the Alliance.
Meanwhile, Tyrande Whisperwind and Malfurion Stormrage grow impatient regarding liberating Darkshore from the Horde's control, ultimately choosing to begin the offensive on their own, against Anduin's advice. In order to maximize their chances, Tyrande undergoes a ritual to turn herself into the Night Warrior, the avatar of Elune's most wrathful and warlike aspects. To counter this, Sylvanas orders several Night Elven heroes who fell in the Burning of Teldrassil to be raised as Dark Rangers to bolster her forces.
The tail end of Legion saw the introduction of Allied Races, which introduced two new races for each side to play as. Battle for Azeroth introduces more, with Dark Iron Dwarves and brown-skinned Orcs included in the upcoming choices. Blizzard hasn't confirmed much about what other kinds of races might show up, but there's plenty of datamined info out there for those who want to take a look. Allied Races start at level 20 after a short scenario and players can earn a special set of cosmetic armor if they level the character all the way to 1110 without buying a level boost.
If you love running old content for transmog items, you'll love the new legacy loot system. Whenever a player enters a dungeon or raid where they are 10 or more levels above the content, the dungeon or raid bosses drop an amount of loot equivalent to what would have dropped for a full group when the content was current. That means players could earn loot for five people in dungeons and loot for 20 people after soloing a raid. The legacy loot system also drops other gear types, like cloth dropping for a plate wearer. It's now much easier to get the transmog gear you want, and you can also collect gear for your alts on the same run.