-Gameplay- Gameplay has largely been stripped down to be a shell of its former self. This trimming has been going on for several expansions, but now it's even worse. Classes only have so many buttons which has resulted in very little skill involved in PvE (even PvP is a faceroll for most melee, lacking any sort of depth and decision-making as it's pretty clear what buttons to press in any given situation) and it's become more of a gear check. This expansion gave zero new abilities to classes, only took them away.
Update: The reason for less experience from gathering is due to how Blizzard revamped professions and broke them down by expansion. In order to get full exp from gathering you'll simply need to find a profession trainer for the relevant expansion. (WoD you just mine or herb the first one ypu come across and the game gives you a scroll for learning WoD gathering).
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 mysterious gates of an abandoned Gilnean castle, navigate a war between elementals and more.
Tiragarde Sound and Stormsong Valley are both fairly similar zones, but Stormsong is a little longer, meaning that you might not even have to finish it to hit 120. Tiragarde also comes with a bit of a warning. There are plenty of side quests to do in the zone after you finish the story quests. Don’t do them. It’s not worth the time or the experience you’ll get.
I wouldn't buy Zygor guides. As a player since path 1.10 (around 7 years now) Ive seen a hearty wow community flourish through each expansion. I am a huge fan of the add on, Carbonite quest. It provides a pumped up version of wow's internal quest database. Also, its recommended to research your servers economy for making gold. http://www.powerwordgold.net/ is a great site for tricks of making gold. Pair it up with http://www.theunderminejournal.com and you'll be on your way to making fast gold to provide for all them alts :P
If you're in a big hurry to hit the end do these two things, run each dungeon at least once and complete the quests inside them, dungeons give HUGE amounts of experience for their quests last I knew and que for a battleground every so often. While it's not the fastest leveling, it mixes things up a bit and gives you a break from the grind, and if you're not crazy into the story it's a huge grind.
The Broken Isles are unique among WoW continents in that you can progress through zones in any order you want. Once you have made it through the initial quests in Legion, you are free to move about four of the new zones — Val’sharah, Azsuna, Stormheim, and Highmountain — as you wish, with enemies, quests, and rewards scaling to your level. The fifth zone, Suramar, is mostly locked away until you’ve reached a certain point in the story.
Most of the time you spend leveling will involve questing and slaying monsters, but there’s also a lot of travel. Travel earns you little experience (you do gain a bit for discovering new areas), so it’s wise to keep travel to a minimum. The new level scaling system, which scales zones to your level within a preset range, helps with that. You can choose what zones you want to experience and stick with them until you finish their quests.
My second most anticipated new feature in the Tides of Vengeance update is the Battle for Darkshore Warfront. It’s the second cyclical battle between the Horde and Alliance, in which each faction takes turns gathering resources, fighting in a pitched raid battle and then controlling the Darkshore zone. In what I hope will be an improvement to the Warfronts feature, the controlling faction will gain access to diverse world quests in the zones they control, rather than the “kill x of y” quests from when it first launched.