Firstly, the mana based attacks on c/m are very strong -- against dodge players. They are based on physical damage and patk, but deal magic damage -- like knight holy stirke damage is magical. Thus they cannot be dodged by rogues using evasion -- very good for finishing off low hp rogues. Also don't forget about feedback drive or w/e, the temporary damage reflect, + the elite skill that reflects dmg when you parry.
Secondly, if you can find someone who doesn't move around much, like a tank or healer, or a tower you can auto attack them. With forge buff up, that lets you spam your rune pulse b/c chain drive activates.
Rune overload is pretty strong if you can supply the rage for it -- sardo item set skill energy supply is good for this, along side rage potions, VN cape, and dalanis set skill energy restore. That plus kinetic burn make champs in general one of the strongest aoe classes, at least for sw -- the ability to clear towers and/or groups WITHOUT NEEDING the 60 elite makes it strong.
There are some item set skills that don't use as much rage, or none at all. Clone conversion works like the mana attacks i mentioned earlier, and it does a lot of damage. Dissassembly step only uses 10 rage iirc, and ultimate desturction has a cast time but 0 cost.
If these options aren't available, then you're better off trying to support/distract. As alreaqdy mentioned, cast high-energy barrier on priorty players, key rescue to reduce dmg received on a friendly target (it can be cast on others).
I'm not a fan of champs myself b/c of the limit on attacks per second, but they can be very effective if you learn how. C/m is argueably one of the hardest classes to kill, and has the ability to dish out a lot of damage b/c of that.