"Who had been represented there?"
Very interesting...so how do we say "who are these people?"?.....like this? "wer ist diese Leute?"
Just to add something to this discussion...I don't believe in English we distinguish between singlular and plural when asking who either. 'Who was represented there?' could be asking about a single person or many people. You would have to make the question more detailed to specify; for example, 'Which people were represented there' vs 'Which person was represented there'.
Wer sind diese Leute is the correct translation for your sentence. But in this case the object is Leute and not wer as in the first sentence which is singular.
OK. I understand. But again, if you want to say "who had been represented there" and you mean many people then, however, you must say "wer war dort vertreten"??? OK, what about this case- Three students were represented in some evening. After a while the teacher is asking to the class "I know that three of you had been represented in that evening, tell me who had been represented there?". So in this case we say "wer war dort vertreten?"?.
OK. that link explaind it (that in the case ,that's mentioned above, we use "wer war....."). But there was another example "wer kommt alles zur Party?" (when we are asking many people to come to party). Could you explain it more detailed? (if you don't mind, of course).