I wrote a brief duelist build with notes on it for some of my guild members,
here is the link
Anyways, I would not reccommend that you get uppercut and counter until you have more tm points to spare. This is because they use many tm points. Also uppercut has a long cooldown, thus it is not spammable. You can learn it, however if you master both skills, you may end up delaying the mastery of your third Job AoE skills.
Hyperbeat lvl 10 is needed for Guard, so go ahead and learn it.
I currently find duelists more versatile than champions, they may not hit as hard but their AoE's make boss trials much easier.