I think Silent Dusk would be useful if Selene immediately stopped whatever she was doing (90% of the time it's casting Embrace) and executed the player's command right away. Lack of responsiveness from both fairies is a huge reason why I don't like SCH as much as WHM or AST- it feels like I'm fighting my pet instead of just being able to focus on the fight. The silence is more situational than helpful, certainly. But I never use it as-is because Selene's too busy shaking her butt to cast Embrace when it's really needed. I'd rather see that issue addressed first and see what improvements can be made afterwards.