Dual blades daggers for all classes?

I'm a bit confused as to how the dual blades weapons are used. I read that most of them have a limit to the ''thief'' class, and as far as I'm aware, blades take the place of a shield, correct? So is it possible for a shadower to equip the dual blade weapons to buff their weapon attack? (I think they should but I doubt this is true, doesn't hurt to confirm though).

Also, apparantly a level 25 legendary dagger that is available for all classes was released, can say, warriors equip that in order to increase their weapon attack? I can just imagine how invincible they'd be...