[Ryuzaki]

Jenna laughs in an unsettling manner...

Kensei can be nerfed when Ghost gets its main class stats. Duelist as a whole is fine, just build crit evade, smack some chainmail on and laugh as your opponents can't damage you nor rely on their bonus momentum, as Fern and Spo pointed out.

The reason Kensei seems OP is because people keep fighting kenseis on flimsy builds, with no def or crit evade. Dodgy punchers, for instance. Or even worse, other kenseis. But, as Spo said, it's not all that hard to handle if they can't crit you, or worse can't even hit you.