Yeah, there is no real "dungeon complete" exp. Technically if you want to calculate exp/hour and NO ONE was doing roulette (which these days, someone is your group is always doing it), it makes more sense to quit the dungeon before the final boss. The exp/kill on trash mobs is great if it is of appropriately level. The boss exp is "not worth it" other than for saying "hey, look at me! I completed the dungeon!"