Well, I'm not sure about the english version, but the german one basically asks you to give your commendation to the person you enjoyed playing with - I always took that quite literally and am only handing out commendations if I indeed enjoyed playing with that person.

That can be the person whos dealing the most damage, but it doesnt has to be. Name, Race, Gender, Glamour, Attitude... all of those can be a huge factor too.
I never thought of the commendation-system as something to actually get feedback about how well someone performed. So of course its extremly biased; thats intended. The game doesnt ask you "Who do you think was the best player in this run?" but "Whos company did you enjoy most?"
So if OP and their friends arent getting any commendations from randoms, it might be because those randoms didnt really enjoy playing with (any of) them, even if they performed well.

So no, I wouldnt say that the system is broken - people can enjoy playing with other people for different reasons. Commendations arent feedback in regards to your skill and you're not entitled to them just because you out-dps'd everyone. They also dont influence anything in the game and no one can see them expect for yourself, so they really dont matter (and yes, I know about the achievments - personally I'm hoping they'll add new ones at somepoint).

Commendations were in no way added to highlight good players from bad players - if that were the case they'd actually be on display for everyone to see somehow.
Its OPs assumption about the system thats wrong, not the system itself.