Okay, first off, I tried searching for this and didn't find any other topics, although I guess some have already been made, this thread is in case there have not been thread about this.
We all know that headshots are pretty much instadeaths in DF, as they shatter the skull quite often, which causes instant death. Now, I have seen my animals and my dwarves get in fights all the time. They normally only bruise each other, sometimes one of the animals will bruise a lung, but they never break a bone bigger than the ear or a finger. Then one of them gets a lucky head shot in and kills the other one out right. I don't think I have ever seen them break an arm or a leg or a rib.
My complaint here is that it is much easier to break a leg, an arm, or a rib then it is to have your skull shattered. Also a punch shouldn't outright shatter the skull nearly as much as it does, most of those hits in real life would lead to various bruises, fractures, or concussions, almost all of which would not lead to death.
So my point is that the head should just be made tougher, atleast as hard to break as a arm, and hopefully more so. I think an arm would be sufficent as I have hardly ever seen one of those break in unarmed combat.