Buff Caustic

Sweaty movement mains: Oh nO I pUsH iNtO ThE GaS AnD DiE. ThAt'S nEeD To bE NeRfEd!
Actually, Nox never got up since he been stomped into the floor at his own takeover event. For now, his tactical is useless. You can't push using it it cause they take too much time to prepare and significantly sell time to be destroyed. You can't defend with it(unless you are already at godspot without windows and 1-2 ways in) cause gas damage is easily: ignored, outhealed, evaded by destroying.
The trap must stay trap: they're big and easy to notice in the open, so the punishment for triggering must not be diminished. Destroyed trap must rise it's cloud damage to maximum instantly and cloud must stay at least 5s or "safe" disarm must be impossible. That will make trap real slowdown, and not a shooting dummy.  

Ultimate damage must be full from first tick or increase without limit and without dependence from number on ticks taken by enemy - so push in it will be real risk at all time.
Such power can be balanced with: scanned/pinged traps be forever displayed to scanner team, until destroyed, Seer/Catalyst tactical able to trigger traps in their AoE, Gibby dome/Catalyst ult/Rampart cover able to create LoS block for gas, Crypto drone able to see through the gas, Newcastle revive shield be impenetrable by gas, and in many other ways. And if with all the counterbalance measures and his large hitbox Nox made it to the last ring...it's your problem.