That black has been pretty freshly painted by the looks of the side opposite the red circle and the way the paint is flaking off, factory paint doesn't do that. I'd be very surprised if it's Robinson's fault, they do make a relatively soft tail rotor blade but they aren't designed to withstand continuous exposure to rocks or sand and operated in a normal environment, many blades will go to retirement. I think there's something that you, other pilots who fly the machine or the maintainers aren't telling us.