Yeah, I was a little bit scared at first too.
But it turns out with 30 cards, 4 shield is just about right. With a 25% slimmer deck, 33% less shields isn't so drastic. And at the thicker size I had too many shields.
I've been grinding the same gods with this 30 card version as the fat 40 and 47 card version previously posted. It's success rate seems pretty similar, and the games go much faster.
I think the original version with all of the extra healing had more EM's, but that's about it.
I tend to prefer slimmer decks anyway, and if testing proves this to not be quite right, we can mess around with the ratios, but I think the one I posted is pretty close.
I was most worried about not getting enough air quanta for sky blitz, but I haven't had a problem yet. I may add an air pendulum or tower in the future for such things.