The story is not fleshed-out enough,
This I agree with.
Joshua Graham is not fleshed-out enough, and it's far too linear because you can't help the White Legs.
These things, I do not. Joshua Graham is just about as fleshed out as the Dead Money companions, Ulysses and various major characters from the main game, and he's certainly more fleshed out than anyone from Old World Blues. As for the White Legs, why would they want or accept your help? Being able to side with the White Legs wouldn't make any real sense from a narrative standpoint as they're brutal scavengers, they only see the Courier as a target because that's how their tribe functions. You're given the option of indirectly assisting the White Legs if you really want to help them.
This ^ But I never got any of the FO3 DLC because they all looked liek crap.
The Pitt was surprisingly well written for a Bethesda product, although it has nothing on most of New Vegas' DLC, I'd only rank it higher than Old World Blues. Point Lookout also has its moments if you pretend you're not playing a Fallout game, it looks and feels like it belongs in a Lovecraft game and not Fallout.
I'd say that at least the Pitt is worth a shot, it's shorter than Honest Hearts, but I felt that it was the best of Fallout 3's DLC because of solid writing and actual role playing.