Fireflies description doesn't match tooltip/debuff mouseover tooltip

In skill tree tooltip description:

Increases max and average damage of critical hits on target.

On the tooltip when cast on an enemy, it is a double negative, thus confusing and counterintuitive.

-45% ... critical hit damage reduction

If you must use the double negative because it is technical, then description should say "Decreases damage reduction (or resistance) to critical hits on target."

 

i do not really know what it does.
In the past it reads, that it would increase critical chance on target. Now, it reads it would increase critical damage in the description. But the effect stated -xx% critical hit damage reduction. Whatever that means.

What it does?:
- increases critical chance on target (offensive)
- decreases critical damage from target (defensive)
- increases critical damage on target (offensive)
and for what it is valid, melee, ranged and/or spells?