Chaos Inoculation Damage Bypassing Mana with Eldrich Battery

Was running the Chaos Temple and Chetza the feathered plague boss fight LVL 46 and I am Lvl 90. Took damage that completely bypassed Mana and directly hit life when I am running Eldrich Battery and Chaos Inoculation that killed me. Unsure how this should work but it is my understanding that all damage should be taken from Mana first and then from life if it is empty. In this case I had over 2k mana remaining when I died.