Having different people play totally different characters doesn't matter when it comes to mocap or voice work (Gollum, always masked characters in real movies, etc.) The only thing that matters is the sound and motion work.
When you have to totally paint peoples skin, they look crazy, and it's not meant to look odd (Tropic Thunder) then it gets weird. Conan had Aziz Ansari on his show recently, where he talked about the Indian dude on Short Circuit. He didn't realize the guy was white until he tried to find him later in life or something.
I doubt the game industry can't be as bad as Hollywood, I'm sure all kinds of people get work for voice acting (though the two top guys may get a lot of the good stuff). Laura Baily is a well connected voice actor, and she must have impressed ND enough to get the part. That doesn't matter though again because of the nature of voice work, and being able to play any kind of character.