There is some kind of sense to allow any build to backstab with any weapon if you are in position and have the talent. Its not something thats difficult to do... although maybe rogues could get some kind of bonus damage and other relatively smaller effect to it.
So every point invested in rogue skills would give a few percent bigger backstabb damage and ... something else. Crippled status maybe... damage to physical and magic armors... weaken status... something to differentiate rogues as better at it then other builds.
