In regards to quitters

[SummonerSenah]

You can't kick AFK players out. A few members of my FC and I were doing Praetorium last night for story purposes and one of the tanks AFKed from the start. So the rest of us left rather than try to defeat all of the bosses in that dungeon with just one tank. And it's not like Praetorium is even a good dungeon for farming tomes. I think in a situation like that I'd rather take the 15 minute penalty than waste a lot more time only to fail at the end.

[RhazeCain]

Supposedly there will be a "vote to kick" option added at some point. So that people can remove a problem player rather than leave themselves. Won't fix all or even most situations, but a few. For example: You're a tank in a low traffic dungeon. 1 person in your party is really bad. You cannot hope to succeed while this person is in group. If you leave, the whole group is done because there won't be another tank with "Join in Progress" in a reasonable amount of time. Vote to kick would give possibility to keep the run going.

Also, the whole leaving thing is vast majority caused by Duty Finder. Easy to join, people you'll likely never meet again, thus easy to leave. Join a FC/LS group and leaving like that almost never happens.