After playing Caustic for about 2 hours to get a bit of progress on "Win with 8 Different Legends", and I can honestly say Caustic is in a really weird spot to me. Because he's really good at locking areas down, obscuring vision, and just making close quarters fights a massive pain to win. The gas damage is really nice, and people still fear triggering barrels.
But at the same time, the barrels take so long to deploy, and the fact that people can spam the bottom to insta-destroy it is pretty annoying. Plus, sometimes people just walk by the barrel itself and it never triggers. Or they just go through it full speed and it doesn't obscure vision and does barely any damage to them.
I think if I were to change anything, it'd be to make the barrel itself have two different functions. If you hold down Q and wait for the animation, it makes a standard barrel. No changes there. But if you just tap it you'll throw out a mini barrel that starts spewing gas immediately upon hitting the ground, it starts and stays at 5 damage per tick, and its duration and area of effect are at least halved. Gives you more aggressive and reliable gas placement options while still maintaining Caustic's ability to lock down areas, you'll just require a little bit more time to put down the standard barrel.