Patch notes are too vague to discern how I feel, since the exact punishment isn't listed. I think a 10 minute punishment might be acceptable per 3 withdrawals, but 30 minutes would be too long.

Don't give so much hate to the people who fish for in-progress queues. Sure they are insistent on it because they get their dungeon clear faster, but if there wasn't a motivation like that, then no one would queue in progress. People would feel much angrier about people who quit, even if that person had legitimate reasons for leaving. Right now most dungeons/trials with missing players can replenish their ranks fairly quickly, and it should stay that way. If it's so annoying to have people withdraw, make the process smoother for both parties and make a separate queue for only in-progress dungeons (with the option of queueing for both at once).