The Graham in Hoyle isn't even "voice acted" though. It's only text. The character conversations in that game are entertaining to say the least. I love the conversations between Graham and Roger, and Roger and Rosella in that game. They are actually well written, and king's questy. Alot of nods/references to the early games in the series.
As for MOE, no one really knows why Roberta chose faux english voice casting in MOE. I asked Mark Seibert, who helped with the casting, and he doesn't even know, why Roberta went that direction. His speculation was at least for Graham, having it, was maybe because other characters had been casted with that accent.