The Elemental system is literally being dammaged by said element, not what it does.

For example when attacked by a fire elemental, you are burned, when attacked by a lightning elemental you are struck. But if an enemy who absorbs those elements is hit. then they are healed.

However, I think the Ice and Water elements weren't thought through in this otherwise excelent game. For Water, you are surrounded by a bubble and slammed to the floor, and for Blizzard a block of ice appears above you and drops on your head. See the problem? It's not the elements themselves that course the damage - it's the impact. So enemies that absorb these elememnts should still get damage.

They should have done these differently. Use the other FFs as an example.