Nothing is free. Assuming you farmed a complete set with a group of 6, you're looking at a minimum of 375 man-hours assuming you don't have any failed runs. I'm not against grinding out gear I want, but it would be nice if you could trade those hours/months for some entertainment at the same time.
I'd still like to point out the glaring gap between the rewards for floor 80 vs floor 100. Personally, as luck based as this event is, I'd probably take my chances with floor 100 given the odds. Breaking 5% success rate would be better than 125 flawless runs at floor 80.
If I couldn't get a group to beat those odds I'd probably give up. It's a game and the purpose is entertainment. I guess I've just worn the grind nerve out when it comes to events that don't put out in a reasonable amount of time; events that are enjoyable being the exception.