And I agreed with you, Ragnarok. I could see a harpy using the throwing rock thing as a retreat. They start with their more standard swoop down, swarm and attack in melee combat, but as the party is winning, THEN maybe the last one or two retreat and throw rocks as a supplement.
But those rocks shouldn't cause 8 damage. 1d4 Improvised Weapons damage makes sense as a "I'm retreating" weapon.
What I don't like is that the rock throwing bit is their primary weapon of choice, and it does 8 damage on a regular basis. It's their primary tactic for pretty much all but 1 of the harpies. Only 1 flies down and tries to kill you and the boy at close range. We should see all four flying in and swarming right away. Then, after two or three die, the survivor(s) then flee and throw rocks to try to ward you off.
And another thing. Why NOT allow enemies to retreat/flee combat? Once you've beaten them to a certain point, let the survivors flee if they can get a certain distance away or something. Do all enemies have to fight to the death? If we can flee, why not let the enemies flee? It has been done in previous games. It can be done here pretty easily.
