DoTs: Assuming that the mob is going to live for certain periods of time, it is worth it to place DoTs up. If the mob lives for at least five seconds, cast Pain. If it lives at least seven seconds, cast VT. The ideal time to cast DoTs is when it would be replacing Flay, but you can substitute Blast if the mob will live longer. Make sure to cast Bolt on cd though!
Take breaks. Unless you're straight up no-lifing it over a weekend or something, this leveling process is going to take ~40 hours. But any time you do need to step away, log out. That tiny little bit of rested exp is insignificant...but you never know when something might come up and you'll have to leave for a longer period of time than you expected. Better to be logged out and safe(especially with War Mode on) than AFK waiting for a d/c. Plus, you'll need to stretch, eat, shower, and maybe sleep. XD
Congratulations on reaching Level 120! There are a myriad of new things to do. The first thing you should do is head to your faction hub ship where you have been doing your mission table quests and footholds to pick up and complete the quests necessary to unlock World Quests. World Quests will provide you an opportunity to grind reputation levels, acquire gear, and gather Azerite. There are tons of new things to do that we will cover in our Level 120 Battle Guide found here: Level 120 Battle Guide.
For collecting artifact power to level up your Heart of Azeroth necklace, island expeditions are unbeatable. There’s a weekly Azerite goal that you need to meet through the expeditions, and when you do, you’ll be awarded 2500 artifact power. There’s a small chance that you’ll get weapons from completing expeditions too, but they’re not a reliable source of gear.
Instead, go to Timeless Isle and take the portal to Gorgrond. From there, fly to your respective faction starting zone(Frostfire Ridge or SMV), go to your garrison, and do the quests to unlock your garrison(A short quest chain beginning down near the water where you'd otherwise start after the Dark Portal scenario). For now DO NOT collect any more treasures than absolutely needed to buy 2 experience potions! Treasures continue to be worth superior exp/h all the way to level 104!!! You don't want to begin collecting them until lvl 100 or later.
Do quests and complete the story of your first chosen area before returning to your capital to scrap all of the equipment items you acquired. You should be around Level 113 by the time you complete your first area. Before selecting your second zone, head to your faction hub ship to acquire your introductory quests to the mission table and your champions. Complete this introduction and then pick up the quest to establish your first foothold in enemy territory.
Allied races: Our new allies will join the factions and players will be able to unlock the ability to play their race. There are 6 planned for launch. Horde: Nightborne, Highmountain tauren, Zandalari troll. Alliance: Void elf, Lightforged draenei, Dark Iron dwarf. Additional races are planned for the future. Receive a Heritage Armor set, if you level an allied race character to level 110.
Highmountain tauren - "Descended from Huln, brave hero of the War of the Ancients, the Highmountain tauren honor the spirits of earth, river, and sky. Though the Legion invaded their lands and sowed seeds of distrust between them, the tribes of Highmountain stand united once more. At long last they are ready to venture beyond their sacred mountain and stand beside their kin from Kalimdor, lending their nobility and strength to the mighty Horde."
I'm very, very interested in a guide that takes into the following: 1) Dungeon finder; and 2) Heirloom items. I've never helped with a guide before, but would be open to help in collaborating on the project. With the leveling guides I've used (primarily this one) I, too, find that I level at a rate that throws the pace of the guide way off (not its fault at all, I can't say enough good stuff about the guide) to the point that I get frustrated and just queue up for dungeons.
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.