I think the balance issues on Allied side are restricted just to british faction (not a surprise, the faction is young and made for money on a pay-to-win engine
).
Centaur needs a little bit of nerf, commandos need rework, churchills still have issues balancewise. Also there are some abilities like Air Supremacy which are totaly broken against OKW faction. On the other hand, British arty kinda' sucks.
I think if Relic will work some more on the british side, things will be better eventualy.
With the ISG, there is a serious problem. I don't see a nerf without doing something about the allied base infantry wich was seriously buffed or without doing something about volks at least if not grens also.
Alternatively, instead fixing volks/grens, for OKW the MG34 should be better in some way (quicker supress or serious damage buff) and for grens G43s should be a viable upgrade.