You could just Ash and use Fatal Teleport, with covert lethality dagger. I use it in the index, and the only thing that can stop me there are mines.

If you're in a pub, people don't usually just stand around waiting for abilities. If they participate at all, they'll likely just be flying around laying people out without you. In your specific situation though, and with what you have outlined:

Atlas Petrify

Banshees Resonating Quake You'll be killed, and scream would be a better CC. Resonance is always nice too.

Embers World on Fire (Firequake) Not strong enough

Equinoxs Rest (Calm and Frenzy) Will probably irritate people and might freeze people out of the way or in unreachable places through bugs

Excaliburs Radial Blind

Frosts Avalanche or Ice Wave (Ice Wave Impedence) Avalanche gives survivability which is cool, but I don't think ice wave will be strong enough

Garas Spectorage or Mass Vitrify

Harrows Condem

Hydroids Undertow or Tentacle Swarm You're not standing still really

Inaros All abilities

Ivaras Quiver

Limbos Stasis and Cataclysm Will probably annoy people unfortunately and makes killing slower

Loki's Radial disarm

Mags Polarize and Counter Pulse augment

Mesas Shooting Gallery

Mirages Prism Too slow, just use her 1 and 3 and forget CC altogether honestly

Nekros Terrify Makes them run from you, which even with augment is annoying

Nezhas Firewalker or Divine Spears exposes you to danger, and puts the enemy up in places that make it harder to headshot

Nidus Larva takes time to build up to the point where you can actually kill something and everyone will have run past you by the time you do, if you're just using larva only you could use it though you'll probably run out of energy

Novas Molecular Prime

Nyxs Chaos Can put enemies in weird places and make it slower

Oberons Hallowed Ground or Reckoning Not the best option for an exterminate, it would be a lot of casting. He's strong otherwise though.

Octavia’s Resonator Usually people are just running through as fast as they can, this would probably do pretty little

Rhinos Stomp

Titanias Lantern

Valkyrs Paralysis You're better off with eternal war and just slaughtering everyone before they come into contact with your team and using that as CC

Vaubans All abilities People move too quickly for most anything besides vortex, but that would be limited

Volts Discharge Maybe, but its not strong enough really to kill people and suffers from freezing people in places that might make them harder to kill

Zephyrs Tornados Slows down killing

I don't think you need CC, but if you have to do it I would probably pick Harrow. He puts people in an easily headshot position and can do a lot at once. Counter pulse mag would work too, though your probably better putting up her 2 as well. M prime is very good but the slow might irritate people.

If you want to help though, I think the best thing you can do is provide buffs through rhino or maybe banshee. That would speed things up a lot more than CC would I think.