Now I, not completely sure I have facts straight, but samurai swords (katana/bokken) are like the swords one use in kendo right? In kendo atleast stabbing attacks are extremely effective, since they are so fast. However, the attack animation is more like the flamberge/polearm one, but the character is standing up straight. (to be honest the current 2h overhead stab seems pretty unrealistic to me) Now Im pretty sure katanas were used for stabbing too, it would deal some damage if someone got stabbed. (even a screwdriver can kill) However, currently the katanas/other japanese weapons are balanced with the "low thrust damage" or the "not able to thrust" ability. If they got the ability to thrust they would have to get a reduction in other abilities like cutting damage or speed.