Even when barehanded, UNLESS their offhand claw is filled with something, like an orb or shield. (yes if it's a weapon and you get disarmed, they'll still dual wield it.)

That being said, only felar assassins get the potential to do a full six attacks (i.e. second and third attack practiced) other assassins only get three attacks while completely barehanded.

Being barehanded makes you slightly harder to parry against foes who are also missing their primary wield. A hand to hand specced warrior with ironhands will have a greater bonus than you have with unarmed defense (and thus will negate an assassin's bonus if you fight one) but it's a similar bonus.

Any race but felar is better off with a weapon in the primary, or dual wielding. You don't attack with your offhand (unless you're felar) ever. If your offhand is free you can use Backfist, but your primary hand shouldn't matter for Backfist. Felars being the exception to this rule, can both dual wield claws AND get backfist attacks, can mix it up when needed with better results than non-felar assassins as far as potential number of attacks goes, especially if you've done some fighting against mobs while barehanded.

Anything beyond that is tactics on your part. Felars pay for the dual wield bonus stat and vulnerability wise as part of game balance. On the other hand, you can use staffs, spears and even two handed swords and still get claw attacks. (Just not backfist if you're using two hands to hold your weapon.)