Death's Dance passive vs. Graves AA

Healing is reduced to 33% for AoE damage.

Grave's AA, which is an AoE attack, not single target, heals for the entire 15% against a single target.

The heal reduction is supposed to apply regardless of whether or not you hit multiple targets with your attack, and so is intended to be 1/3 as effective if you only hit one enemy with an AoE attack (because you get more healing by hitting more than one enemy).

His autos are not single-target. While they can only apply on-hit effects to the same enemy once per shell, other enemies hit by pellets will take the full force of any on-hit effects as well. There's no argument to be had. It's an AoE attack and should have its healing cut down to 1/3 for Death's Dance as intended.