FF Tactics: War of the Lions

[Masquerade]

OK. This game has been giving me nothing but hell since the very beginning, but somehow, through diligent training, I was able to make it pretty far. All the way to this castle to rescue Alma, as a matter of fact. Unfortunately, I got stuck on the roof when the Marquis and his two assassins attack. The goal is to defend Rapha, but get this. The Marquis attacks her with Doomed Aspirations, one assassin charms the main character successfully, and the third assassin (who is dual wielding) kills Rapha. Game over. All of this before ANY of my characters got to make an action. What the HELL? Does anyone have any ideas about how to get past this stage?