Yes, and that's why the Jailer is dumb. If he actually went after someone who was already stronger on their own, he would've had a much more formidable servant than Sylvanas. Like Thrall, or Jaina, or Malfurion, or Tyrande, all these people who already had incredible destructive capabilities. Not Sylvanas, who is just some random archer.
But oh well, I guess only Sylvanas could be dumb enough to get manipulated by Satan. So maybe it's not all that surprising.