I'm reasonably sure the "Offensive Slow Defensive Ability" in this skill doesn't do anything - it's pretty hard to test for.
... but, even if it works, it's still pointless. Archers aren't affected by their targets' DA anyway.
It would make more sense to lower the enemy's Offensive Ability, but I have tried various methods and there doesn't seem to be a clearly working way to do that with a passive skill. The only thing that works is to blindside it by raising the Archer's DA.
Something that does work and is sort of in the spirit of the skill is "Retaliation Slow Attack Speed."