My first thought would be that this would work just fine even if it were reduced to two turns of damage inversion. You would just wait to use it until you were almost dead, then unless your opponent had PC you get ~3 turns of additional life. It's like a Dim shield, but with less counters (works against poison, bolts, etc) and it's less effective if used before you're already low on hp. It's not so much something that you'd chain together, but rather a card that you'd include one or two of to extend your life in a pinch.