Rumbler is arguably the best ranged weapon Ogryn got. You can snipe specials with it, and you can CC bunch of things with it.
But this has anti-teamwork problem that its smoke lasts longer than GG’s, so it makes your team have hard time to see through it.
Especially, it gives Sharp shooter hard time to snipe shooters.
I think Rumbler needs short, and small smoke like GG, since contrary to what Dark Tide emphasizes, it interferes with teamwork.