@Kampfarsch
That's how the gantz ball work. It doesn't take into account the "experience". It doesn't give a chance to train and getting used to it. There is not a concept of fight the minion first, get exp, end with the final boss. But usually at least the gantzball take into account the amount of participants, giving missions that involve huge amount of aliens to bigger gants-team sometime even making them co-op with other teams. This is the only "fairness" the gantzball is able to process. Everything else is all left to the dices.