You would be surprised how effective Sturmpioneers are against M3's. At max range, no of course not. You can just walk away when the M3 is trying to snipe the sturmpios.
There's no reason to build Volks against Soviets until you can afford a Shrek.
Go double or triple Sturmpioneers + Kubel against Soviets. Deals with anything early even against M3, but it can get a bit tricky. But so long as the Sturms are in cover, the Sturmpio insane DPS will just shred the M3 and force it off. Don't even bother with the Raketenwerfer, and Volks are only really worth getting for the Shrek. Though I like to have Volks against US.