Assassin stance gives +2d6 sneak attack dmg. The PrC in question gives sudden strike +4d6 (which only flaw compared sneak attack is that it is not triggered by flanking). You can get assassin stance via feat and it stacks with sudden strike (as both sudden strike and sneak attack can be triggered same time in same situations expect sneak attack works also in flanking).<br/><br/>But true that PrC is not greatest and does not give otherwise much.