I acknowledge the strong fighters in the challenge event, like Zero who cleaned up all three areas.
Not to discredit the results, I believe that each player should nominate one area to participate in. My team isn’t strong enough for Advanced, but I might have a decent team for Beginner and Intermediate. I should choose between these two and once I choose, I should be locked in for the event, no switching. I see other games do this really well, to encourage top players to compete higher up, but provide opportunities for those with weaker teams to compete for some good rewards.
As the OP states, balance. This game still needs to improve in that area.