I would like to start by stating that I do agree with the intent behind the changes made to Samurai in 6.1 however...
I feel the way their intentions were implemented has turned out to be less than ideal. Let's breakdown the reasons why.
First the Kaiten removal. As for the animation I personally won't mind the loss of it but I can certainly understand why some people will as it added "flavor" to the job itself. The potency buff effect itself really didn't matter to me and I assumed SE would just passively up the potency of the iaijutsu to compensate for the loss of the ability itself, and reduce the kenki generation so as not to make this a massive buff with too many extra shinten. I assumed wrongly, in large part I suspect because of the auto crit change that happened simultaneously. Speaking of which...
Because of the auto crit change I'm pretty sure SE needed to either reduce the potencies of the iaijustu, OR reduce the potency of everything else in the kit in order to keep this a neutral-ish dps change. While I do agree with the end effect of lowering dps fluctuation and overall making dps more consistent, the path they chose sort of damaged the "identity" and "feel" of the job itself.
Make no mistake, the job as it is now is perfectly functional. The damage it does has only ever so slightly been reduced, and patches going forward can always tweak potencies here and there to adjust the damage of a job. But... from a satisfaction standpoint the job itself doesn't feel as fun to play. I understand this is largely a subjective experience and while I cannot speak for everyone I'd argue most people view the biggest "mechanic" of Samurai to be its iaijutsu. You literally do a set of 8 gcds into your 9th gcd that has a whole special animation and cast time to it. The core of the job is centered on iaijutsu usage, that isn't really a debate. But NOW after the changes to potencies even with auto-crits your core button for your job doesn't have a large "impact" or "oomph" to it. If you look at the potencies of Midare versus either Gekko/Kasha, Midare is roughly 1.5 times as strong as them AND has a 1.3 second cast time. Essentially you get to the end of your 8 gcd setup and then wind-up a Midare and think "I did all of that just for... this?"
Now... I will admit iaijutsu still is a ton of our overall damage, and as stated previously Samurai is perfectly functional. The TLDR is Samurai is less satisfying or interesting, and these changes could have been done differently with the same effect while retaining the fun factor for this job.