Nice. I have always had Mihawk > Shanks, so I have never had doubts Shanks or Rogerwere swordsmen.
I mean, Roger bloody called his son as his sword; anyone who though he wasn't a swordsman was coping big for the usual reasons.
As for Aramaki, I think it's because of his "inspiration". Gennai Aramaki, from whom Aramaki of OP takes bot name and appearance, was kind of a "secret (good) swordsman":
So I think Oda Is doing the same in OP style.
Also, there Is the things that if a top tier Is keeping a sword around, this thing should be very well used in his fighting style.