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.
Balance: Moonkin Aura - Starsurge grants 4% spell critical strike chance to 8 allies within 40 yards for 18 sec, stacking up to 3 times. Feral: Leader of the Pack - While in Cat Form, you increase the melee and ranged critical chance of raid members within 40 yards by 5%. Leader of the Pack also causes affected targets to heal themselves for 4% of their maximum health when they critically hit with a melee or ranged attack. The healing effect cannot occur more than once every 6 sec. Guardian: Sharpened Claws - Maul increases the damage done by your Swipe and Thrash by 25% for 6 sec. Restoration: Overgrowth - Instantly applies Lifebloom, Rejuvenation, Wild Growth, and Regrowth's heal over time effect to the target. Hunter
This Addon solves that issue where you have 5 Paladins in your Raid and no one can decide who is Buffing what. It has a little UI that represents Different Classes in your Party or Raid. You can change what buffs you want to give out then just mash the Class Button for each Class type until they all Turn Green. If anyone is missing a buff you are assigned the Class
Our old friend Quest Helper isn’t updated for the client, but there’s !Questie and MonkeyQuest to help you track available quests and their objectives. The biggest challenge to leveling up in the beta is searching for where the quest objectives are, so if you’re looking to hit the level 30 cap fast — or just the level 5 cap in today’s stress test — you’ll need one of these.