To be honest the only faction that incorporates more than 2 mgs into their builds in any reasonable level of play is usf. But I would be very shocked to see codguy asking for a nerf to allied forces 
Here is the thing.
USF .50 cal serves its purpose, it's just as good, and just as effective.
Even though it's strong, it's main purpose is an offensive support unit, just what the maxim should ahve been btw.
I have yet to see a .50 cal spam.
MG42 is good at absolutely everything, it's better than a maxim, can be used offensive just as defensive, and rips the shit out of units at vet 2.
YES MG42 IS OP, I say this as somebody who has spammed maxims and mg42 in the majority of my matches, my strategy was all about spamming mg > 222 > StugE, and I used to rank about 68 as ostheer before(and I still rank better with axis than I do with allies).
But the axis defense force will just come and bash you whenever you tell them that it's op, because you know? what's op are soviets... better nerf the maxim again even though its crazy bad.
So yeah, I kinda love it when they tell you soviets are cheesy, op or complain about maxim spam even though you can spam mg42...etc ostheer is just as much if not worse in terms of cheese.
OP you ask how to counter mg abuse?
Try hard.
Once you open with tier 1 and sniper, you will never do a game without snipers against ostheer, I promise you that, but learning how to micro a sniper takes time, you will lose countless games until you figure out how to apply pressure while preserving this unit, because once its dead, its gg.
If you chose to go tier 2, then remember that Zis guns is the absolute mg killer, if you have the luckiest of rng you can one shot wipe an mg42 squad.
As USF it's even easier mind you, if you can endure the game until you can mass lmg or scotts then hmg will become a burden more than a tool in their hands, because microing it will become a risk in every engagement.
Last you have lieutenant with smoke grenades than can help tons, regular grenades are also good (the best grenades in the game after guards nade I think), but it will cost a lot in your resources flow.