There has been a small number of quests where the whole group did not get credit when the main did a mini event, and there has been a number where they did. So far when Ive done 4x mini events at the same time, the game did not spawn or create 4x the content. It just went once and they got credit, This was the first that triggered simultaneous spawning. I did not get 4 extra helpers either, Just one. I attribute my surviving this event to being level 77 and fairly well geared. I do not think I would have lived 4 levels ago and missing half my blues.