From looking at the trailers and info, I'm pretty confident this game will be balanced. Every faction will most likely have advantages and disadvantages relating to the kind of creature they are. For example elves would have strong archers but weak cavalry, or orcs would have weak infantry but other strong units.
Plus, one of the reasons they're running a beta is to sort out balance problems. So I'm not worried.
Edit: Sorry, other people have basically said the exact same thing I'm saying.