From what I can tell you're talking about how it should be , but you also state you haven't tried the 30min gem quests. They're specifically the ones that are bugged. If you haven't already, please try the 30 min ones a few times - I did 5 today and not one had 9 mobs, and one of them had 0 mobs in the 3rd wave. But, the twice a day ones, the ones you've been doing, yes - they're fine.