Watch these two screens to see my oneshot-backstab build.
Force and Air Sigils on the daggers, Bloodlust on bow.
Basically what to do:
Pop ELITE, use STEAL (enemy is stunned), use '5' spell, use '1' to backstab (18k on GC-Ele). If they aren't dead yet make sure to use you '2' spell, heartseeker, to finish them off.
You are extremely squishy when using this build so use your stunbreaker wisely. When fighting a Guardian, remove his aegis with you bow before you use the elite-steal combo.