@BarretOblivion my dear, my dear... I don't have to look at a reddit page for mains. There I will likely find a lot of what is written here: A lack of coherent arguments.
What you say is only half true. I can only go with what I witness in-game. And in-game I see that a vast majority of Caustics play passively and try to rely on their gas to do the work. If there is a select few that do otherwise, I believe you, but that percentage is awfully underwhelming. And I bet that this proactive play style is paying off a bit more than the passive one.
The major problem with Caustic is that his suggested play style is hard to balance by proxy. Camping is an advantageous way of playing the game and usually yields better results. And unless the guy who camps is screwing up hard, most fights are in his favor. I know that is because I camp occasionally as well. By adding things like extra blocking factors or defense factors, you make it more frustrating for the guy who already will have a disadvantage to storm a place. Does that mean we have to remove it entirely? Not at all. But I'm saying that the advantages shouldn't bypass a certain threshold. Which it can very easily do. If you use Caustic for a different play style than what he's originally meant for and it works out a bit less beneficial for you, then you gonna have to deal with that.
Caustic's biggest disadvantage right now is his hitbox. And I don't know how many more times I have to mention that until someone finally acknowledges it, but if his hitbox was smaller, he'd be better in general to a point where he becomes more usable outside of buildings. Additionally, I'd also be up for letting his gas affect targets for 2 seconds after leaving the gas. That would always be a guaranteed 15 damage, plus additional time revealed, plus more slowdown time. So you'd always have a guaranteed 2 second slowdown, DoT and reveal. Fair deal for offensive use aswell.
Bloodhound is already deemed overpowered, and seeing how is usage rate is raising rapidly, he will eventually (probably) end up being nerfed. Caustic's usage rate was also rapidly raising, going from 'Seeing him occasionally' to 'Seeing him every second game' - He ended up being nerfed. So I don't see how this comparison is in your favor.