Why aren't you bringing up more of your own troops in the meanwhile? If there is a sturmpio in a building it's not going to be doing anything, ignore it until you have enough units near by to deal with it.
We'll use USF as an example. You'll have a riflemen + Rear up about the time that he has a kubel + Storm attacking you. You'll have a second rifle building around this time. His volks will be building around the same time too.
So you'll pretty much try to stall until your second rifle comes out. During this time you may not even get remotely close to that building while a Kubel pelts you. So you're defending some random part of the map while he gets out and possibly flanks you. Seems like a bad spot to be in.
I feel like the biggest problem is the Kubel sometimes outranges infantry for NO REASON. Like my infantry won't fire at the kubel but the kubel will fire at them. Then, you got a 22% chance to penetrate it each shot while he starts taking models, it becomes a bad time.
I find myself having the best shot with brits, because the Universal Carrier is just as retarded.