For the Greater Good...
I did find that some of the armies, particularly the Necron, seem to have distinct advantages over some of the other armies, but if you have ever played the table top game, you'd know that the armies are unbalanced, thats how it's supposed to be. The fun and challenging part of the game is picking an army and learning to use it strengths to overcome its weaknesses and eventually kick the living snot out of everyone else. Try playing with each different army and you'll notice distinct advantages and disadvantages to each one, if the game seems to easy, change your opponent, or change your army, or just bump up the difficulty level, the AI set to hard can definitely provide a challenge to any gamer.
So go out, get Dark Crusade and prepare for hours of carnage, because in the future, there is only war...