My idea was for the gas to slow humans like creep does, in addition to muddling the view of lightly armoured humans. So you'd still get extra protection for wearing more expensive armour, but the basilisk would also still be useful against everything as a support class (plus it'd fit in with the movement restricting ability the basilisk already has). For consistency's sake the poison effect ought to be dropped entirely (touching a booster would add it back).
Global sounds for lucifer cannon charging make sense, but I'm not sure how useful they would be; it's almost always obvious when an lcannon is charging, if not necessarily how much one is charged. But yea, since the tyrant never shuts up it'd probably be fair to make the lcannon noisier.