And people have touched upon this in the thread already. The majority of those groups are either people who really DO know what they're doing and just want it done, or someone who wants to be carried. I've personally seen both, join some and wipe for multiple 60 minute periods. Join 2 others the other day and both one shot him. And the thing is, even WITH those rules, people who can't complete the content still join, since you can't tell what someone's skill is without seeing it first hand. In any case, there's still nothing wrong with making the rules, ignore them or join them, your choice. It's meant to TRY and keep away the people that know they are inexperienced and will mess up from joining.
