Also note that power leveling is sometimes used to refer to paying someone else to level your character to cap as fast as possible (i.e. they power level for you); a distinction used by Blizzard is to refer to the paid leveling as "power leveling service." This behavior is against Blizzard's Terms of Service. Power leveling yourself, which this article covers, is perfectly acceptable.
He goes on to say that the changes went too far, and that they have "no desire" to keep moving in that direction. The problem is they don't know how to fix it quite yet. Hazzikostas understandably says that they don't want to make blanket changes that miss the "real source of the problem," which is exacerbated at levels 60-80 when the leveling curve gets particularly punishing. The sky isn't completely falling though based on data: Hazzikostas says that leveling is 15% longer. In the short term they want to increase experience gained at these levels to soften that blow.
Leveling from 58-80: Outland and Northrend Recommended leveling paths for level 60-80 players in WoW. Includes best zones in Outland and Northrend, as well as notable quests and rewards. Leveling from 80-90: Cataclysm and Mists of Pandaria Recommended leveling paths for level 80-90 players in WoW. Includes best zones in Cataclysm and Mists of Pandaria, as well as notable quests and rewards. Leveling from 100-110 in Legion How to level quickly in World of Warcraft Legion from 100 to 110. Includes heirlooms, assaults, useful items, and experience boosts. The Big Bag Guide This guide covers bags from drops, quests rewards, vendors, and professions. Additionally it also covers item type specific containers.