First of all, I just wanted to say that I thought Erin and Daniel were fantastic guests! I loved the energy they brought, and I really hope that they can be brought back sometime in the future.
In defense of John Cusack's accent work, or lack thereof, I have to admit that I was totally cool with it. The movie had already made the decision that English was going to equal Roman/Latin, but back then, just because someone was "Roman," didn't necessarily mean that they were "from Rome." The Roman Empire stretched from the Portugal to the Middle East and from the British Isles to Africa. Once a culture was conquered by the Romans, they weren't expected to completely abandon their native language, so I'm sure that a pure "Roman accent" would be pretty hard to pin down. I mean, how many accents are there in the America? Hell, accents can change within the same state.
So, maybe, in the world of Dragon Blade, to show a difference in class, Roman's born in Rome - like Brody's character - have English accents, while Roman's born in Gaul or some shit have a more Chicagoan, every man type of flavor.
The fact that they all sing in Latin still makes no fucking sense though...