If we're having only four classes, I don't know if we want a lot of races unless they add something to the classes, like certain classes would be given varying aspects for fighting and defending. Like trolls would be be slow but sturdy with defense. And dwarfs would be nimble but not terribly strong. If the classes aren't key to the story (since we will focus on offline as well) I'd rather stick to human, troll, maybe elves? I think keeping things simple would be useful, if we were doing things purely online, then it would be a different situation of course.