Download the game right now, create an account (a new one; not your old one, if you were a previous player), and you’ll be able to level your character all the way to 20 for free. There are other annoying limitations placed on this free experience, but it’s still a great way to familiarize yourself with the world, see if you enjoy the experience as much as you were hoping, and get a feel for the different classes before you settle on a main one to play as for the next 100 levels’ worth of gaming.
The idea of the expansion came up after the heroes of Azeroth dealt with so much external threats like the Burning Legion. In their own words, "so when we talk about what's the biggest threat in this world, is it the titan or is it the dwarf paladin that put a hammer in that titan's head"? As such, the enemy (at least during the early parts of the scenario) will be the opposite faction, a "vast army of world-destroying forces".
Allied races are variants of existing races. The Void Elves are a version of Night Elves, while the Highmount Tauren are, you guessed it, a version of the Tauren. Four allied races are already in the game before launch and two more, the Dark Iron Dwarves and Mag’har Orcs, were added after Battle for Azeroth launched. Each Allied Race has its own racial abilities. You can also unlock a heritage armor set by leveling any Allied Race to the level cap.
Azeroth paid a terrible price to end the apocalyptic march of the Legion’s crusade—but even as the world’s wounds are tended, it is the shattered trust between the Alliance and Horde that may prove hardest to mend. As this age-old conflict reignites, gather your allies and champion your faction’s cause—for Azeroth’s future will be forged in the fires of war.
Meanwhile, on the island continents introduced in the Battle for Azeroth expansion, players level 110 and above who have unlocked world quests can participate in Faction Assaults. These special events, alternating between Alliance and Horde territory, will give each faction a chance to band together to defend their territory or invade their enemy’s via a series of world quests. The prize? Survival! Also faction, gear and gold. Maybe even some pride.
The expansion brings a major change to the PvP ruleset on each realm. Every realm by default only allows players to attack NPCs in the open world; players who wish to engage in world PvP now have a setting called "War Mode" that can only be toggled on or off in their faction's capital city (i.e. Stormwind for the Alliance and Orgrimmar for the Horde). While in War Mode, players have access to new talents and abilities, as well as a slightly accelerated rate of XP gain. Characters with War Mode activated are only able to see other players with War Mode, unless in their own capital cities.
“I think that there’s a lot of gray in the game and in our world, right,” asked Cobo. “And so I think that tapping into that and making things reflect the complexities of the relationships that we have between these key characters and then the player itself, and having the player be able to experience that from their perspective, is really what is one of the strong connecting hooks of World of Warcraft.”
Anyway both got to 110 at around 50h played. I messed up with my Pal by going to Legion once I hit 100 instead of finishing treasures and bonuses in WoD. All in all, if I picked the best zones and was only trying to level as fast as I could, I would probably could have done it in roughly 40h. Note that it would have a been A LOT faster with a Monk as both Ret and Rogues don't really have a decent AoE until 40+ (45 for Ret and 63 for Rogue I believe). The daily also helps a lot. I know that leveling my Monk before the pre-patch was insanely fast. Might be slower with the changes to FoF, however.
You should try and quest efficiently - pulling several mobs if you can handle it, using your burst cooldowns while questing to kill everything faster. Many people would think that a 10-minute cooldown like Bloodlust is useless in open world, but you can do a "kill-15-mobs" quest in like 30 seconds if you pull a lot and use it. A free quest every 10 minutes is not that bad.