I couldn't agree with you more. Even if removing Kaiten hasn't changed DPS by a huge degree (around 3% maximum in a crit-buff heavy comp), the class now feels like a crucial part of it is missing.

Kaiten bridged the gap between your normal abilities and your BIG ANIME FINISHER. The extra damage boost led to some massive numbers, which were always fun to see. Not to mention that the animation for Kaiten seamlessly transitioned into Midare. With the new potencies and lack of kaiten it now there feels like there is hardly any difference between abilities. I finally settled on SAM because I liked the playstyle and the class fantasy. But the changes really do a lot of damage to the fantasy of the "one-cut-man" that Samurai is supposed to have.