The PPS42 hardly imbalances the game. It's just an additional SMG choice for the Allies, not another SMG class. It's slightly better at longer ranges than the -41, that's it.
The MG42 doesn't unbalance the game either. You haven't played enough with it to determine that. It being good does not mean it unbalances anything. The MG34 is also good. It's just another MG option, like the PPS is another SMG option.
There are only two tanks in the game and they need to be balanced. They seem quite balance to me except at very long ranges where the sloped armour of the T-34 is most effective.
Except in real life the PZ 4 F2/G with the 75mm long barrel could penetrate the T34 at quite longer distances than the T34 could penetrate it in return and the sloped armor could do nothing about it. And the T34 had a lower rate of fire as well, but this should be equal in the game for balance.
Most of the time I play the Axis team is full of veterans. I usually have to completely carry the Allies team by either putting up a huge score or taking TL/tank role and doing an awesome job in order to win. In these cases it is clear that if I wasn't on the server Allies would have lost. This happens most of the time I play. If I play Axis it's unfair and noticably way too easy to win - not fun. The Axis is mostly stacked.
That's your anecdote, and games are not to be balanced around "teamstack", that is the most inconstant vague nonsense there is.
The maps are also majority Axis biased. Please see my thread on it in Ideas and Suggestions forum.
They aren't at all. You might only get this feeling if you play on some non-campaign servers with a certain set of maps.
What about all of the Axis heroes running around with the PPSH-41?
Unlike tons of Russians running around with MG34's, that is completely true to history as they were captured and used in significant numbers by the Germans together with other foreign weapons they could get their hands on.