Since when is it an average ability? It does fantastic damage quickly, from a very good range, and dependent on luck, can quite easily wipe team weapons.
Well done, you just contradicted yourself. You yourself say it relies on luck and no, it doesn't do "fantastic damage". When was the last time you played Soviets and used the ZiS? Because I have a feeling like you haven't at all if you're saying what you're saying.
As a solution, couldn't be possible to gives Zis barrage a shared cooldown for all Zis and keep it performing as it is in live?
If you want a shared cooldown then the barrage would have to be made basically OP to justify butchering it like that.