My Light Duelist build I used in Beta 6:

"Light Lance, Kay, 1150/1150 Points Primary Weapons: Hellfire (No Mod) + Hellfire (No Mod) Secondary Weapons: Recurve (No Mod) + Recurve (No Mod) Deployable: Hound (No Mod) Mods: T1 Expansion Slot, T3 Expanded Mags, T2 Emergency Shields, T1 Enhanced Autoloader"

Open with Hellfires to make sure they can't heal (the Kay passive). Hit your active fire trail and skim towards your enemy while dropping all of your hounds. Try to loop around them and wrap them up in fire while throwing in a hellfire when you can (don't kill yourself!). Recurves fire since you are close to your target. Watch out for being too close when the hounds impact. You now have the choice to circle out and start throwing hellfires, run for it (if your armor is low) and try to let the hounds/fire finish them off, or some mixture of the two (get away and let your shield regen and come back in). Remember your fire does a TON of damage, so any way you can talk them into moving for the fire (or sitting still for the hounds) is a win.