Curious why so many want a Katana class to be tank, the weapon is very effective vs unarmored targets but you could do better with other weapons if you were going to abuse it with parries. Katana in general is a rather brittle very sharp weapon, you have to revere it because otherwise it's going to get rekt'd lol. That and many other reasons would be why you can find a lot of examples with Samurais with spears and bows, at least from what I've gleaned they were pretty practiced with the bow perhaps sometimes more than the katana. Spears and Arrows are good against armored targets while a katana would be when you lost or couldn't use or other items.. or you were teaching a civilian a lesson as known to happen.
It seems the weapon kills and killing can equate to DD and can be qualities of a tank, but not generally what I would think is the spark idea to make a tank- I guess I'm not seeing what everyone else is connecting Samurai with that makes it tanky. I get it is a game so you get to stretch stuff, but normally you stretch things in the direction they were already going "man fearless of harm to himself from a tempered rage" goes into a game as a tank with some logic (even though in real life it wouldn't matter if you were fearless, no armor means bad tank lol).
They can ignore the reality of the weapon, again cause.. game, but maybe if it must be a tank then they give a nod to the weapon- perhaps some sort of lore and gameplay mechanic of using aether to give the blade a soul for such frequent defense. Would work with the Samurai sterotype I think (bushido/soul of the blade). Also you could use the tempo of the blade's soul (given by game mechanics) to decide if the job was in defense or damage mode, like warrior or paladin can.
tl;dr I understand that games don't need to mirror reality, but I really feel that gliding, evasive, unarmored deadly makes a DD over any sort of damage soaking idea.