Ryzom

If you want to maximize your healing power in groups without having to designate a second healer, have two heal spells -- one using sap and one HP. Alternate between the two heals as needed. Using both meters will effectively double your regen. Very efficient at lower levels.

At high levels, things reverse, and it actually becomes less efficient to do it this way and more efficient to use one spell that takes an equal amount of HP and sap.