I completed the event two days ago, made a team that did 10 to 12 runs per key, with 0 defeats. I didn't feel harmed in any way, I just found the dungeon challenging.
But of course, just like in real life, I agree that it would be better if we received all the rewards of the game just by pressing a "redeem" button and that's it, congratulations! You are the most incredible player here.