I've only played a couple of times, but the last time was recently. So, indeed, the Champions won't really get a chance to attack properly. Because their speed is worse, and if their morale isn't good, they won't be able to attack effectively – by the time it's their turn, the opponent will already have blocked them, and there won't be an opportunity to build up momentum. That is, the Champions' advantage lies in the initial attack, a hit-and-run.
But, of course, it's probably great for quickly taking down neutral creatures:D. As for the Knights, I won't say anything; in my opinion, everything has already been said about them many times.