Not sure why so many people join dungeons simply to leave 1 sec in, but I see it way too much, and have been seeing it since 2.0. There really needs to be harsher punishments for consecutive dungeon abandonment.
Something I was thinking is to give characters an invisible "Leaver Counter" (or something like that) which increases each time you leave a dungeon before it is completed. And the more "stacks" you have, the harsher the punishments become. Starting at 30 minutes, as it is now, and just increases the more "stacks" you have from leaving. And because people could simply do nothing or "disconnect" and wait to be kicked so they don't get punished for it, being kicked could always give half a "stack", 0.5 instead of 1, but not give an instant punishment unless they have a certain amount of "stacks". And the "counter" would only go down while you are logged in, and at a SUPER slow rate, and get entirely wiped each week.