|Mathwei ap Niall|
The Kensai might have poor strength, but he is adding his int to CMD (as a dodge bonus) so he isn't all that vulnerable to disarm.
Having the ability to see in the dark and see invisible are good plans for a Kensai though (and I'd argue that while Kensai might be slightly more screwed when they can't see, pretty much any character is screwed enough by not being able to see that the difference is neglible).
Which is why we said to use Bluff. A simple bluff (feint) strips the Kensai of his dex & his Int dropping his CMD against a disarm to 10+bab+str and as a 3/4 bab class with the tanked Strength most Kensai have it's pretty much an automatic disarm (or trip, or bullrush or literally any combat maneuver you want). With every realistic combat maneuver build taking improved feint it's always a sad day for Kensai's.
For a 2 feat investment (improved feint & Greater Feint) a Kensai is effectively a sitting duck for the entire opposing team.
No, with all the glaring weaknesses the Kensai archetype has it's at best a glass cannon with a huge crack in it and if you yell boo at it it shatters.