I don't think there'll be a huge Order vs Disorder imbalance in the game. The fact that the classes differ so completely from side to side is going to make people a lot more interested in rolling across that faction line. Furthermore, both sides will have elves right from the start, and if causal players like one thing, it is sexy, sexy elves.

I'm interested to see the balance within the factions though. Empire vs High Elves vs Dwarves, and the Chaos vs Greenskin vs Dark Elves. And what kinds of troubles might arise from that.