Burnacid; When you used that lightning, did you check your enemies shield? There's one that reflects spells. Also, dimensional shield only stops physical damage. Hope that explains it
I personally don't have any problems with health. You run round the early enemies without taking a hit, then when the bigger enemies come, you are better equipped to handle them. Although I agree 4-5 of the fireball ones in different parts of the screen is really annoying. 4/5