I suprised nobody sayd it (at last I didn't found such topic),
but smoke barrage is totally useless - there are no situations where it's helpful.
When your teammates needs it and your commander call for it, it arrives too late. All teammates will be dead for the time it arrives.
And if you need smoke, you can just use 1-2 smoke granades and it will be enough, and you don't need to wait for barrage arrives.
And as commander you almost always have better options for calling support, like helicopters or warlock. Сommander also not always have observer to callig support as it is, so it's bad idea to waste calling possibility for just calling for smoke.

So I suggest 2 ways to make it useful:

1. Let the smoke stays for much longer. So if this wave didn't waited for it arrives, went without it and dies, next wave will go through smoke which still not dissapear.
2. Let smoke barrage don't waste support calling possibility. So if you just called for e.g. warlock, you still can call for smoke barrage just after that, without waiting for cooldown.

It will be really easy for devs to make this I think. Upvote me if you agree please, for devs notice the topic.