Power leveling is the process of handing over your character to another player (usually it's a seasoned WoW player), who then gets your character to the highest level possible in the shortest amount of time. In essence, someone else does all the hard work for you so that you don't have to waste your time by leveling the character/s yourself. And as with most other MMORPGs, there are a lot of players who offer such power leveling services for World of Warcraft.
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.
Heirlooms are special pieces of armor that level up with your character, so they have stats that are always respectable for your character’s level (up to level 110). Heirlooms that fit the head, shoulder, chest, legs, and back armor slot offer an experience bonus. The total bonus is 45 percent if you have them all. It’s also possible to acquire a ring that adds another 5 percent, but you must win a fishing contest acquire it, and that can take some time.