MechaTarrasque
Hero
Where does this story come from? It seems like something you're just making up right now. No offense, I just don't see it.
Anyway, the Blade Pact is just as much a magical swashbuckler, or shadowdancer type, as a magical assassin.
A shadow dancer isn't a magical assassin? Don't tell the 4e assassins, the existential crisis that they aren't really assassins might be too much for them.
As for the rest of your comments, the story I mentioned is the villain's plan. In most books, it doesn't work. The patsy escapes, proves the prince was evil, either discovers he was the long lost heir or marries a princess, etc. If that doesn't sound familiar, I can't help you.
I know when the warlock comes up, people on this forum like to pretend "connotation" isn't a real word, but they are wrong. The connotations of the warlock are one of the big drivers of WotC's design of the warlock. WotC isn't hiding this (see http://www.enworld.org/forum/showthread.php?539947-Insights-into-Warlock-Invocation-Design for more details), so if you are looking for what the warlock is designed to do, sneaky bad guy stuff is it. A warlock might be a good guy using bad guy toys, but they are bad guy toys. And as far as the bladelock goes, it is a pretty poor sneaky bad guy that hangs around in front of the angry mob with a sword. Of course, some people still expect the rogue to do that too, so there is no helping that.