A lot of players seem to be having a hard time figuring out how The Huntsman works. The last patch fixed it so that your flaming arrows will show up as just that when you get a kill with them. Before players would see a flamethrower icon and it was throwing them off.
Make sure to have a Pyro light your arrow or you can shoot someone that’s already on fire and kill them. Either one of these ways will give you the flaming arrow kill. Another tip to using The Huntsman is to make sure you don’t keep the arrow strung for too long.
You have about three seconds after you reach maximum power to let loose your arrow or you will lose the accuracy of the shot. This is why a lot of players are having trouble aiming or having arrows that seem to fly off into the distance. If you’ve had it strung too long and want to pull the arrow back in you can right click to release the tension.