Character: Paladin, Level 61 (LE Beta 0.8.3d) - Last Epoch Build Planner
It looks like if I use Judgement and the mana cost takes me negative, I don’t get any damage from pious offering. Based on the wording, I’d at least expect the bonus damage for my remaining positive mana. Also, using it with any amount of mana from 0-40 does the same amount of damage.
E.g. Mana cost of the skill is 43, if I use the ability at 40 mana, it does 1200 DoT ticks, when I use it at 45 mana (so would expect a minimal difference), it does 2350.