I'm by all means no lore expert, but the whole samurai thing is from Doma right?

Which is where the Au Ra come from...

Since Dark Knight makes sense with the Xaela lore being that Dark Knights abilities are said to come from watching panthers.
(DRK mount description) So them being nomadic and hunters etc..i can see the relationship .

Wouldn't Raen clans leading a more solitary life wouldn't need to be so heavily armored and be a tank?
Their naming conventions are even based on old Japan so clearly I think it's safe to say we can associate samurai with the Raen.