What I read in the Steam Forums is that the voices/accents used in the game are options..... meaning you have have them in English with accents or in their native language.
To me, it's not a "Serious" concern.... it's not a concern at all.
Think about it:
If you want realism, then realistically, you would be an actual german or russian who can speak and clearly understand the language as if they were speaking english.... most of us can't and thus, we're like a foreigner fighting amongst a different country's troops, not actually being a natural part of that force & understanding what is being said.
If you don't know what the rest of your team is shouting other than reading text in the bottom left screen, then to me, that takes more out of the immersion than having them speak in your own language.
Someone else mentioned BC2 where the Russians are by default, speaking Russian.... there's no text to read on the screen, so you never really clue into half of the messages & thus, a disadvantage to the fluidity of the gameplay & team work.
If you don't speak those languages and don't understand those languages, where's the logic in having the gameplay with those languages? Realism and Immersion?
Ok.... how real is it to be fighting in an army where you don't understand a single thing anybody is saying to you & have to read text on your screen, further taking you out of the immersion, compared to just hearing a request/command with your ears you can understand and doing it without having to take your eyes off of what you're doing?
I'd prefer to have them in english with accents, so I can understand what people are saying and not have to take my eyes off the action.