The term swordsman is relative in one piece. It's a freaking pirate theme almost everyone uses swords duh! As the term swordsman what qualifies as a swordsman the attitude,portrayal, title/label, or just using the sword without Haki? Either way they all use haki hence why there's different type of haki and classification. Just because you don't act like a badass swordsman or have that mentally or cool personality doesn't mean you're not a swordsman. Shanks and Rayleigh obviously are sword wielders and they obviously know how to use it. In other culture, mythology and even current swordsmanship the ultimate art of swordsmanship is not using a sword at all. A weapon is the extension of your body fact! so do you consider jedis swordsman?...since they don't use a traditional sword. Just to make it simple anyone using a sword is consider a swordsman because that's a fact u dont' have to act cool and mellow to be a swordsman. Dragon>Gorosei>Rayleigh (rusty/old, but for all intended purpose and overall experience etc)>Shanks>Blackbeard(if you include DF user)>Luffy's Grandpa( thought he's raw haki, but he does use a sword just rarely ever)>Mihawk>Shiryu>Vista>Zoro(obviously at the end he'll be on the top 5 strongest people not just swordsman)>Law. For specific classification of swordsman Gorosei>Mihawk>Shiryu>Vista>Zoro>Law. (dragon,shanks,rayleigh and other conquer's haki user wouldn't belong here for practical comparison).