The pre-Legion version, where you passively amass stacks throughout the game, and you can later drink in combat to regain mana.
As a Mistweaver main back in WoD, I really loved this broken OP mechanic, and I am very pleased to see it make a return. Although Blizzard did not specify whether Mana Tea would be uninterruptible like Hunter abilities, as it was back then.
Thoughts?
Mana Tea has been redesigned – For every 25,000 mana (at level 70) you spend, you gain 1 stack of Mana Tea, with a chance equal to your critical strike chance to generate 1 extra stack. Activate to consume 1 stack of Mana Tea per 0.5 seconds to restore 3,000 mana (at level 70) and reduces the mana cost of your spells by 50% for 1 second per stack of Mana Tea consumed after drinking. Can be cast while moving, but movement speed is reduced by 40% while channeling.