Little bit OP is some ways, but balanced in others. Shield is useless after you quanta reaches a certain point. I really like it, but I think you should lower the max quanta point you have now. 35-40 is too much. I think a better number would be closer to 20.
Edit: Perhaps gravity or earth would be better elements... but then again, conversion of damage into quanta is a abstract concept, which time is more suited for.