Also a keen observation. This is probably the root of COH2's balance problems. How could it/should it be resolved?
For starters we can make it so that caches don't benefit teammates.
Of course the balance is going to be crazy when players are receiving 4 times the fuel without making a single investment. OKW in particular is never supposed to be receiving such high resource income it's no wonder they are so strong in 4v4s where they have a feild full of fuel caches supporting them.
With caches only benefiting the player, tank numbers and pacing for each player would be more like 1v1 levels. And USF won't have to deal with as large a number of heavier vehicles that their AT was never meant to handle.