Yeah I don't know why (maybe to make game more dynamic) they nerfed Caustic's gas damage plus most importantly removed slow effect from it. Since then he is just useless, only thing he can do is scare the crap out of you when you suddenly run into a gas barrel - did so last week and was like "wtf is that... already forgot that legend exist" :D
So imo they for sure need to revert damage and slow effects back to previous state + add a bit more durability to barrels which are triggered.
Nox vision - I still don't get it how it suppose to work, I feel as blind as caustic as playing vs him = basically a bit hindered. Gas should be 1:1 like Bangs smoke just doing damage and Nox vision should be = wallhack. Same as e.g. in firing range you see bot outlines through smoke, Catalyst wall etc.
Then he is good to go as is.
Above mentioned ideas of multiple nades, bigger ult surface area, gas+termite = big bang - sure, sing me up, we will have another Fuse in the game :)
p.s. based on leaked info they actually will buff Caustic and Seer next season? or maybe already this split.