Oh GOD do I hate those flies. They alone are enough to make me lose my temper, and turn my mouth foul, lol.
Not only do they deal too much damage, but they NEVER. HOLD. STILL. Even targeting them doesn't help, and may God have mercy on your soul if you use an Odachi or Dual Swords and try to hit them. Unless you manage to get lucky and hit them, and take them out in one blow, you're in for a horrible time.
Could either all those type of flies get nerfed, or could the targeting system be tweaked a little? When I target them, or any monster for that matter, and try hitting them, more often than not I miss, because even when targeting, your character will swing in the direction your camera is facing, and makes hitting moving enemies, especially those FLIES, a living hell.