While I do agree that Kid sounded a bit too old in the Japanese version, the English voice just outright doesn't fit. That voice sounds too gravely for Kid; he needs a voice that gives off an air of refinement, poise, propriety, and even a little haughty (save for his OCD scenes, of course). Instead of sounding like a prim-and-proper rich kid, he sounded like a 13-year old smoker. The acting felt out-of-place too, as if he wasn't even paying attention to the scene.
Patti's voice was spot-on, at least. I don't think they could've picked a better voice for her, and her giggle is even better than the Japanese seiyu's giggle, in my opinion.
