Only yesterday I wrote about how, despite a previous hotfix, leveling in WoW still feels slow. Blizzard are clearly listening, and Tweeted out today that they've made adjustments of about 14% to those in the 40-100 brackets. Tweet below. I'll let you know how I get on (I've just hit level 40). 

We've pushed a hotfix that reduces the amount of XP needed for most levels between 40 and 100. Note that the new required amounts may not always display properly for the time being. We'll have details in the next hotfixes update.

— WarcraftDevs (@WarcraftDevs) July 31, 2018