As long as you are not outplayed or outgeared, Vengeance destroys almost every class 1v1. And its less squishy than Immortal.
All specs of jugg are viable, just have different roles:
Immortal: guard teammates, taunt, stunlock (charge+backhand+choke)
Vengeance: pick a target, kill it, go to next one
Rage: stay unnoticed within your pack and lolsmash
Anyway if you are fresh 50, you will feel underperforming because of gear with any class, jugg is fine
Edit: whatever spec you play, dont pretend you are a Mortal Strike warrior trying to solo like a hero. Never go alone to a battle, because no matter what class you are 2>1