Pio Spam doesn't really work well at all. They don't stick up to anything in combat except Combat Engineers, and that's touch and go.
If the German manages to maintain a serious level of aggressiveness and out plays you in terms of micro, map awareness and map control, a 3 or 4 Pio build can be ridiculously effective if it has the right support elements.
But in reality if you're facing Pio spam just spam Conscripts and preemptively build some Anti-Tank. They're not going to have all those repair units around and not take advantage of it.
Conscripts out-DPS Pioneers at all ranges, and have more health than them. They're more expensive but they're the most efficient counter because they scale extremely well into the late game.
