Not sure if it's the snapshot thing, but I notice it as Bard where your basic attack is a cast, against Samurais.
I watch their buffs before attacking to make sure they don't have the swirly-wind 1-shot buff up.
They don't, so I press attack.
Mid-cast, the buff will appear. I can't stop the cast, I get the debuff, I get 1-shot.

I've not played Samurai so perhaps there's some Animation that I'm meant to watch for, before the buff appears?
Tbh my eyesight's pretty shit, so probably wouldn't be able to see it anyway. But if not, it feels like there's very little counter-play to this.