As long as there is just one potion slot it is a bit rediculous to have a potion with you that just stops negative buffs. Than you have to choose between heal or debuff. I would prefer heal as long as the negative buff i not so extremly that it lasts for, lets say 10 seconds and do 50 dmg per second.
Really cool it would get with more than one potion and the ability to switch between potion-slots. Than you could have, lets say, 3 healing and one debuff. On maybe 'E' you switch potions an 'F' activates the currently selected potion.