A few more ideas to consider:
A. Healing during battle in melee, you should waste and attack at least and have enough \"room\" to take the potion, even if you setup the hotkey for it...
B Healing during battle in ranged, mages, archers, should loose an attack/spell/action also. Even when there is some advantage in been so far of the slashing they normally will have lesser HP, there is the balance.
C. Healing rate should be different depending on your health and your race. Ex. If a lemur and a Kran get hit, they should heal at different pace, and maybe depending on the kind of hit, they could have some \"pain\" remaining, meaning, for example if they were hit in a leg, their walking will be slowered.