They are too cheap, too spammble, consistent damage, they throw those incendiary grenades like pro baseball players, plus they make the entire garrison/cover play style look like a joke and toward mid-late game are like terminators. Either do something about the STG upgrade/flame nade or make them more expensive to reinforce and call it a day.
Actually, the thing is that Axis mainline infantry is strong early game, while Allied mainline infantry is weak early game. In the mid-late game, Allied infantry is stronger, while Axis infantry is a little bit weaker, but a thing worth noting is this : Axis infantry doesn't drop weapons upon death/wipe (Volks actually), while Allied infantry does drop weapons upon death/wipe. Which means that Volks are fine. Especially in the early game, supported from Stumpioneers.
Gameplay advice : Use cover, deny cover with nades, and in case that he blobs, blob yourself and make a blob showdown. It's that simple. Bring Commandos, Shock Troops, Paras, Rangers, bring Shermans, T-70s, whatever you can. He blobs, you blob. It's an eye for an eye.