I would like to start by mentioning that because of Square's refusal to give us a direct answer as to why they're changing SAM, it's rather hard to come up with alternative solutions to suggest.

Hissatsu: Kaiten being removed was likely to tone down how busy SAM gets during two minute windows. I don't agree with the idea of making jobs less busy in general but I feel like there were far better ways of doing this than stripping SAM of its core identity, (Kaiten -> Midare) such as lowering the amount of times you use Shoha and Shinten.

As for the guaranteed crits - I think along with crit variance what they also wanted to address was SAM being too good into raid buffs. There was also a better of going around this too though, by making Midare and Ogi a lower percentage of the Samurai's total dps without excluding them from party buffs outright. This would lower the importance of critting Midare and Ogi and tone down SAM's output into raid buffs.

The new Samurai gameplay just feels awful, please consider fully reverting the changes and instead slightly lowering Midare's total damage contribution to SAM's dps.