I've not tried the other supposed powerful classes, but I'm finding champion pretty strong.
You get healing spell that can be spammed with battlestandard.
You get 3 summon skills that can give, 3 wolves, 1 sprite and at least 5 acestral warriors. I just recently hit 32 in both nature and warfare and the 5 acestral warriors just slaughter everything in their path along with the others.
You get good offensive skills, and duel wielding can be fairly fun and allow for quick killing.
None of your skills have a recharge time more then 2-5 seconds.