Caustic Main here to give advice on fixes

I too really enjoy Caustic and believe he should be reworked a little to make him feel a little more threatening in the battlefield. The thing that bugs me personally is the fact that his abilities aren't as effective as they should be. His main role in a fight is Zoning, and controlling the battlefield with his gas. The fact that the Nox Traps can be destroyed at the base incredibly quickly is a universal counter to Caustic as a Legend, invalidating him in most Comps because his whole kit is revolved around the Traps/Gas. I like your ideas and I think I know a couple changes that could make Caustic a much more valuable asset in Apex.

Nox Vision

His passive overall feels really limited since you too have to be in the gas in order to see enemies. Instead, allow Nox Gas to "linger" on enemies and have Caustic see them through walls for a limited time (maybe 3 - 5 seconds?). Also, Caustic should get a queue to notify him that one of his traps were set off, because honestly I don't notice half the time. Whether its an Audio ping or a voice line, I'm fine with whatever. This passive also allows Caustic to determine the health of his traps. (see below)

Nox Gas Trap

Alright, lets be honest. His gas isn't threatening. The only reason why is because you can shoot the base of the trap to instantly stop them. My idea to make his traps feel a little more of an issue is to give them a set HP. I'm thinking around 120 HP. This will force players to think about how to deal with traps and spend more time focused on them.

Caustic will be able to determine the health of his traps by the color of the trap's display.

Green = 120 - 90 | Yellow = 90 - 60 | Orange = 60 - 30 | Red = 30 - 0

Damage can be dealt to traps by: Shooting, Melee, and Ordinance.
All weapons deal base body damage to Nox Traps.

Light/Heavy Weapons deal normal damage.
Energy Weapons will be more effective and deal 1.35x as much.

Shotgun Weapons will be less effective and deal 0.85x as much.
Grenades and Arc Stars will destroy traps regardless. Thermite Grenades have no effect.
Melee Attacks will deal 60 damage always.

Along with this change, Players can determine the health of an enemy Nox Trap from the LED on the sides (Green - Red; which are visible through the Nox Gas.)

I feel this change could make Caustic's traps much more valuable and threatening to players. I honestly don't see an issue with the low gas damage, since it ticks through shields and primarily is used for zoning, but I think the range of triggering should increase.

Bloodhound

Bloodhound's Ultimate Ability should reveal the locations of all nearby traps passively, and see them through walls. I feel like this would be a nice counter to the changes I suggested above, (or in general) since it would allow Bloodhound to evade traps more.