You can put people in M3's and just taxi them around to cap, while force-retreating most of what you come across. If you're doing it properly, you shouldn't be losing the capping game.
I don't have a problem with the ZiS Barrage. It sacrifices some effectiveness as an AT gun for that ability, which still costs 60 munitions to use.
Tracking is a bigger "problem" than Barrage, for me. I'd love to get my PaK to shoot at max range without sacrificing capping power by making someone spot for it.
Burts is right, the ZiS-3 field gun was dual purpose. It could function as light artillery by lobbing HE shells at an upward angle, or as anti-tank by firing AP shells at a more directly. Be happy 'barrage' is an ability and not a fire-mode. Could you imagine?