For all the people who say its already in the game RaF, yeah too bad for us who live in countries that are blacklisted for it. And a battle.net country change costs quite a lot if you dont want (or can't simply because you dont live where you want to the destination to be) to send your documents such as drivers licence or ID to blizzard. So either add this or add elixirs that cost in game gold. Maybe even make Quintessential quintet (5 different classes to lvl 90 done) achievement a requirement to unlock the 300% xp gain potion, would still be cool.