You know what'd make these less of a problem? Grace periods.

If I get 90k'd, but within the first minute I try to get back in, I should be allowed back in. Imagine someone waiting an hour for his dungeon, just to get 90k'd and hit with hours in queue. They'd not want to keep a sub up. And fates in HW are giving less than palace, so of course people are doing to use the instance section.