ive found ways of overcomming this for terrains and water / grass. The way i did it was to make sure the entities axses are in the right order. (it seems to sort more reliably than with the verts).
With hair, you could try making sure the axis of each hair is sorted in an outward patern from the head.
With hair, you could try making sure the axis of each hair is sorted in an outward patern from the head.