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.
Cooking benefits all classes, especially melee and hunters (it is a free source of food). Until higher levels, the benefits it provides are almost exclusively stamina buffs. While more stamina is always nice, cooking is not essential to leveling. Considering the time investment required, if you pick up skinning then cooking would absolutely be a wise skill to level prior to hitting your level cap, as beasts often drop meat useful for skilling up.
I've found the best way to level alts is Pet Battling over by Halfhill in Pandaria. My Nightborne Priest I got to 90 that way (the rest was WoD Treasures, then regular leveling post 100), my Mag'har Shaman I'm at 61 with 16 hours or so played. Having a second monitor to zone out and watch Netflix or whatever helps. I think it's the fastest way to get to 90 personally. I really dislike the leveling changes so I just Pet Battle now.
Research instances appropriate for your level online. Running instanced content is the single most important thing you can do, at least up through level 85. Instead of focusing on questing, focus on dungeons. A quick search for “WoW dungeons by level” or similar will help you find the right instances for your level. Keep in mind too that many instances are faction specific, so make sure to check Horde or Alliance specific lists!
I've been having what is apparently a scaling issue caused by inflated secondary stats on some Wrath of the Lich King items. In particular, my Highmountain tauren warrior leveled through Northrend and picked up a green, iLvl 87, 2h sword. All of the secondaries were in the +25 to +30 range, and the Dugi Gear Advisor decided it was better than the heirloom 2h axe I was using. So I went ahead and equipped the sword.
    As it goes with almost any MMORPG, World of Warcraft is a very grindy game. In it, you’ll have to pump your character to the maximum available level before you can get to the end-game content which all players are so used to. And the problem is – the process of going through all the expansions just to get yourself one new class to be playable in raids is very time consuming. Even if you have a vanilla WoW leveling guide at your disposal, you still have to do all the boring quests or clear those repetitive dungeons over and over again. This pattern affects almost every activity in this online world. At the end of your day, you need to really dedicate your time to playing the game or you will get nowhere.
Functionality is the heart of these guides, what you are really paying for.  There are a lot of aspects I could look at with regards to functionality such as; questing path; quest progression; addon user interface; bugs; performance and many more.  All that we are concerned with are questing path (speed) & user interface.  All the other aspects aren’t worth comparing as both wow guides are light in terms of system usage, both have very few bugs, and both update your quest progress in real time.

Discipline: Premonition - Heals nearby targets within 20 yards for [ 75% of Spell Power ], and applies Atonement to yourself. Deals [ PS * BC1 ] Shadow damage to yourself for each Atonement you have active, and increases their duration by [ 5 + 0.1% of Spell Power ] sec. Holy: Rapid Mending - Prayer of Mending is now instant cast, and its jump range is increased by 10 yards. Shadow: Void Origins - Void Eruption is now instant cast. Rogue
We have no idea what implications this might have and whether or not it even indicates anything, since Patch 8.2 is still in testing and a Tuesday launch is more than unlikely due to Essence tuning and Azshara's Eternal Palace, which is supposedly coming shortly after launch. Blizzard said they wouldn't be delaying the new raid like they did with Battle of Dazar'alor.