If he is only doing this to a few hens, then it sounds like they are his favorite. Some people may remove the roo from either all of the hens or just the ones being over-mated. You could also try saddles that are made for chickens. They can come in a variety of cute types and their sole purpose is to protect the hen from this kind of injury. Though if you like to play dress-up with your chickens, you'll never have enough.
The feathers will grow back if given some relief. You can also give a bit of extra protein to the affected hens to help speed up the recovery. You can google Chicken Saddles and you'll find lots of places that sell them at a variety of prices.