Kensai Question: My question to the OP

FredN

.....Ok, I gave some consideration as to why you are even considering this. I know why I am; it was an interesting thought experiment, and I wanted to see how it worked out in reality. But the only practical reason I could see would be to create the world's best combat oriented thief, letting your NPCs wield the super weapons. Yeah, backstab + Kai sounds pretty nice, but setting up a successful backstab can take a fair amount of effort. So, if you want sheer destructive power, you are better off keeping the straight kensai. You can use Imoen, Hexxat or Jan as your party's thief. However, if you really, really wanted to play a thief character but were unhappy with any of the usual builds, then yes, this would be a good variant for you.
.....I have a level 31 Kensai armed with Ravager +6 . He can perform Greater Whirlwind 3x per day, and has a THACO of ... sit down for this one ... -22. Toss in Kai on top of that and opponents pretty much vaporize on round 1, except for some end game bosses. As I said, an interesting experiment, so I am going to follow through with it, at least until I regain my Kensai abilities. But he's not going to be the engine of destruction that my pure Kensai is.