Rob, when you made the draw comparison, was it the values that you compared or the special damage?
My understanding of use of chain shot to destroy rigging and masts would mean you should be getting lots of sail damage and mast damage, which means after 6 sail damage thats a mast gone which cannot be repaired plus other mast damage so if you get a hit in a ship should be disabled pretty quickly as you can only repair a mast once.
I have not read a ship being disabled at long ranges ( here I mean half ruler in game turns) hence possibly why its at the short range.
I will have to look through my C damage counters to see how much mast and sail damage they include.