It seems that the Potion of Chilled Clarity may have gotten nerfed in a hotfix this week, with the penalty for using the potion being made more severe for all healers.
Edit: 11:45 PT Blizzard has reverted this hotfix.
What is Potion of Chilled Clarity
The Potion of Chilled Clarity is a potion that players can use to have their abilities cost 0 mana, but at the cost of 40% increased cast time. However, the key word on this potion was cast time.
