This is caused by greedy selfish people "fishing" for party in progress to get easy tomes and boss rewards and I do aggree the penalty system should be introduced ASAP as it's getting out of controll fast. There is already several threads here discussing this particular issue with numerous disgusting people there trying to defend such behaviour by silly claims like "it doesn't affect those I do not join in any way" or "it was designed that way" and other similar nonsence blabling.