I don't like having two kinds of towers. How about using a mark of Light, 6 Guardian Angels, and nothing else from Light? Then add more Gravity cards.
Edit: I tried a version per what I wrote above. It sucked. Too much defense. Also, in my first game, a single Mind Flayer lobotomized all the Armagios and Guardian Angels as they came out. Without their powers, they are almost useless.