"+% damage to enemies at 50% life or more" doesn't seem to do anything?

[Fulcrum52]

I have a axe with "121% damage to enemies at 50% life or more" and when I compare it with no weapon I only deal 50% more damage and that's because it's a mythic with +42% weapon damage. I stop one shotting simple skeletons a few minutes into a round while also having a "66% damage to enemies at 50% life or more" relic equipped.

[A lungful of asbestos]

Yeah I noticed that stat doesn't seem to do anything. Even if it works, if probably stacks additive with other things. The Oni statues and items with that stat I have tried a few times, seems really ineffective.