The damage to heads is just fine.
I have 10PD + 150wpf + mw-longbow + mw-bodkins and I deal 102 pierce.
For a while ago a tincan with a good helmet surived a headshot from a distance of 3 meters
(And it wasn't rainig)
So I think there is no need to rebalance headshots.
The only bodypart which needs a rebalance is the
hand.
I made a test with a player with 18str and light-medium armor
and I shot him in the chest and hand from a distance of 3-4 meters.
He allways survied a shot to the chest, but he died from 1 arrow to the hand
The hand needs to be rebalanced and not the head.