What about accents? Not every voice actor can do them, you know. And someone who can do one accent can’t necessarily do another. And what level of realism should the voice actor be able to achieve? Should he be as good as Hugh Laurie popping off Greg House’s American accent like he was born and raised there, or should be simply be able to do an exaggerated version of an accent, like Monty Python actor John Cleese pretending to be French?

An accent can be bad as long as it’s obvious which accent it’s supposed to be, and as long as it is strong. However, you have to know what you need when it comes to accents and other aspects of the character’s voice. Even if you don’t know what the voice over talent is supposed to do with the lines exactly, that’s OK. It’s pretty safe to turn over some of the creativity to the voice actor himself. After all, you’re supposed to be hiring professionals.