I do this quite often, but wish they'd make it easier. Extend the time we can remain in a dungeon after it's over, and lower the level of remaining mobs the group left behind, so that if we want to go back and explore on our own, we can then solo the mobs that originally would have taken the whole group.
It would solve a lot of incompatible objectives problems if we could start by racing to the end for players who only want the completion rewards for the boss kill, then those interested in side objectives could take their time going back and exploring / looting the whole place.
