There is an announcement linked to the top of the workshop page that links to changes I made to the mod and how some stuff works now.

Although to sum up Essence of Aura being changed, get you the aura sphere weapons and either kill the enemy in a single shot or make the kill shot with the aura sphere weapons when the enemy isn't colored blue.

Essence of Aura was reworked into "wasted aura" that wasn't used to inflict the status effect that makes the enemy glow blue.

It's a little more lore friendly, and because of how it works, farming it is entirely user intentional. You can choose to farm for it on your own accord instead of having it drop everywhere and filling up inventory space when you don't need it.