Heaven's Hammer + Mage's Ultimate = -MP, 0 exp

I'm not really getting where the confusion is. I said auto kill to imply 1 HP, because that made it sound like the game doesn't apply a "hit" to make it 1 HP. Basically what i'm trying to say is, if you don't hit the monster, you don't get exp. HH might make everything be 1 HP, but it doesn't apply a "hit" to do that, unless it's a boss.

Er, okay...

Reason why I didn't understand it is because it still works if it's not a boss monster, meaning I get exp. The exp just disappears when there's a really large mob of monsters dying at once.