I used to have the same problem as you. Then I learned how to play the class.
You want to spend 40-60% of the time stealthed. Pick 1 target, spike, burst DPS, and vanish. Rinse and repeat. When you get close to death force clock/shroud and bail.
I don't claim to be a pro, but I can usually juggle 2 healers at once which is huge in WZ's.
Between mind control, whirlwind, electrocute, low slash, and jolt it's not difficult to disrupt heals. And 1v1, it's rare my opponent takes me to half health before they're dead.
You have to know what ability to use at the right moment, and track all of your CD's constantly. It's not easy, but definitely possible.