I've never ran out of time in a dungeon while leveling up. The tightest was possibly Qarn with people failing miserably on 1st boss because they had no clue how to dispel doom, which took them 3 attempts to figure out. And we still finished with 15 minutes spare.

The first dungeon I did run out of time was AK when we first attempted it, and we just couldn't get past the wall.