When cast, any spell damage you do to an enemy cause Essence Flux to create blue particles that fly from the damaged enemy to OD.

This no longer makes sense, sine the ability only slows enemies, without granting OD anything. Previously, it was to visualise the mana he gained from it.

That particle effect should be given to the Sanity's Eclipse charge counter. That one gains a charge whenever you hit an enemy with Arcane Orb, or cast Astral Imprisonment on them. So that particle effect would make sense here.