I honestly can't say if it is negative or positive. I do know that caustic was quite op, so part of me wants to feel the nerf on his gas is a good thing.
I've seen a few mentions about people now just being able to easily destroy the tanks. They didn't seem that hard to destroy in the first place so I fail to see how that is a valid argument. Maybe it's just easier to destroy them at doors then, when someone used to have to use grenades, an ability, or risk a lot of damage to break the doors before?
On the negative side it seems caustic has lost his ability to be able to camp. Which I'm finding hard to see as negative, the only reason it would be is because now your team's ability to effectively hold themselves up in a building has been slightly diminished. And if that's really what people are upset about, then I find it silly.
I also see a lot mentioned about his lack of damage reducing buffs? I feel as a defensive legend, he should probably have one of some kind. Maybe a bit more resistance to flames? I wouldn't go as far as saying immune but a resistance sounds nice.
Caustic's gas is either way still yucky and I'd prefer to not be in it as I still see it as unneeded damage.