The DLC that would stand alone best would probably be Honest Hearts and Old World Blues since they open up new, unique environments with great, individual stories behind them that take from the Fallout: New Vegas lore.
Compared to at least two of its predecessors, there's much less openness behind Lonesome Road in favor of concluding Ulysses' narrative arc that made up the overarching storyline of all the DLC. Yeah, Lonesome Road would be difficult to grasp out of context without playing the other DLC, since a lot of the exposition for Lonesome Road was built up over the course of the preceding stories of Dead Money, Honest Hearts, and Old World Blues. I had only played Lonesome Road and didnt care for it much.
