Once a USF player (or more, in larger modes) has 2+ m36s, building a P4 is pointless. If both M36s fire at the same time, the P4 is dropped instantly to 50% HP and forced to retreat.
Well 2 M36s vs 2 vet 2 P4s is actually not that hard to win as Ost, especially if you have panzer tactician and can retreat the damaged one.
The key is getting up close and having munitions for blitzkrieg and smoke.