Heal wounds heals a total of 10 wounds on your followers. It tries to heal 1 wound on each follower, starting with the most heavily wounded ones.
As for flying. It's sort of intended to be sniper from the other side.
- Sniper: Can attack even if attacker is behind obstacle.
- Flying: Can attack even if target is behind obstacle.
You're right in that it doesn't make a lot of thematic sense but it felt like that way the abilities best complement each other.