Well, they can probably also delay arrows, meaning slow them down, and when it's slowed down, the damage is also reduced =)
It's basically an impediment... for visibility.
I think that when there are two "medium" obstacles between the archer and the target, the damage from the shot is divided by 4, and when there's only one, it's halved.
But maybe I didn't explain it correctly, that's why I asked about it.

Барон "Vampires"
Отдай свои прошлые сны,
В сомненьях себя обрети,
В бешеном танце душа кружится!
Не думай, что будет потом,
Здесь и сейчас мы живем,
Стань хоть на миг сам собой, слышишь!