I think a big issue is a lot of is being brought up is preconceptions, and a bit too much picking apart details like logs and how to spell japanese words.
Some see Samurai as the ultimate warrior, others see them right next to the ninja turtles and just a term to describe any japanese noble.
The truth is somewhere between both.
It is also hard to define what a samurai is.
In the west a Knight as we know it likely only really existed for a very short period.
The samurai in contrast have a good 1000 year stretch of history ( little less, but a long time nonetheless ), and most of what they are changed a great deal. When Musashi arrived for example he was someone who just changes history, much like Sun Tzu or Alexander the Great, or Gandhi- Samurai before him were a lot less then those who came after. And yes after him they did fight with dual wielding, and they likely lost that 1.5 times damage bonus you get from doing so. So which 100 year period are you claiming the samurai are from really makes a difference.
Likewise the armor and swords used, which era Samurai are you talking about, there were samurai who had cannons for use on the battle field, really wicked long bows, a monster mace. The did not just use Katanas. The one thing that is always talked about is how well rounded they were, well educated, and artists as well, and capable of dealing with politics and long term strategies. To me this is really more important.
But they also had Samurai who were nothing more than thugs, who had no honor, who were greedy and sneaky and cowardly and incompetant. There were great swords with names which had prayers and took months to make, and there were ones hammered together enmasse and handed to peasants. The samurai is just a term to describe the nobility who served as officers in their armies, much like we use captain and general, and they how great they were really varied, again are we talking about the man raised from birth as a samurai with a blessed sword his great grandfather used, or are we talking about peasant conscripts who just learned they are now samurai.
But regardless of all that, if this is for a game, then i want Musashi, or Samurai Jack, or some of those anime things where you use ki energy to cut your opponents in two. Not because i see this as true, but because it adds things to the game, it is fun and adds style. And if we can get these things working it will actually help fix a lot of issues in the game engine itself which can help the western style melee classes.
A level 10 samurai should be comparable to any other level 10 base class, not better, perhaps worse, and be something which can coexist in Toril, this is already in D&D via Kara Tur, it's just never been done in a way that really works yet.