I've had the Devastating Blow perk for awhile now, but I'm not exactly sure how it triggers. Seems like ever time I behead someone it's not after I did a standing power attack but after I just do a regular standing attack. So is the description of the perk wrong?

bump

It increases %25 damage with it and higher chance of oneshotting enemies.

I think it was supposed to but the same has happened to me in power attacks and non-power attacks.