A rogue that wants to be a blackguard, naturally.Perhaps, but the prc clearly favours some classes over others. What rogue, wizard or bard takes cleave and improved sunder?

The class has a melee focus, but nothing else really hamstrings the skulking cutthroat concept. It has appropriate calss skills and offers sneak attack dice. Not sure where the disconnect is for you guys.Pure fighter classes entering said prc clearly get a lot more benefit than a spellcasting or roguish class. If the designers had intended for the prc to be open-ended, they should have come up with a varying list of abilities to cater to different career paths.
In theory, my character can take any prc he wants. In practice, there are only so many he can take without screwing with his advancement.