Mana Bubble reduces damage taken by one heart instead of consuming mana to reduce all damage or as much as you mana will allow. (Which is what I thought it did.)
Me and my friend are playing a custom modpack with high damage ceilings. (zombie do ~20 damage.)
Could you add a config option to increase the max damage reduction?

Nevermind, I found it in the code, it does exactly what I wanted it to do, but at a high amplifier.