If you dont hit the head constanly, why play sharpshooter? If you cant hit the head constanly, you cant do a damn thing to the scrake even if you are using an xbow.
Axe or LAR the scrake to the head give you and your teamate ~10 seconds to clear those crawlers and clots around him. And if you can still find the head after the scrake is stuned (working on finding the new hitbox myself), he will die faster than you think. Not to mention support can also shoot the zeds behind the scrake without worrying of the scrake suddenly charge.
A not raging scrake is SLOW and are not dangerous at medium to long range. It dont really required to kill him right after he shows. A husk or siren, however, is more of an issue to the team. Also, it is your teamate's job to make sure nothing gets in your way to kill the scrake if you are a berserker / sharpshooter. If you get surrounded when you try to kill the scrakes, your teamates fail. Not you. You keep big guys from them, they keep smalls from you, that's the deal.