I disagree. Even is allied tanks were on par with the axis ones (and they aren't), the high number of AT infantry units that axis factions can deploy makes much more harder for allies to win.
As 4vs4 is a gamemode won by spamming tanks, axis have the upper hand in this mode because all their AT units are way better than allied's. Better micro than your enemies can win the game in the early/midgame, but once reached lategame allies are fucked up unless your enemies were much worse than you.
Simply, and without in any way wishing to wound, 4v4 is currently casual - ofc , some take it to far farther intense levels, and it would be neat if relic could balance , say, 3v3 or 4v4 differently, but unless and until they consciously do, balance testing lies on 1v1 and 2v2 - and ever has done so. (Scheldters doubtless gave this premiss a certain reassurance)