DLC is like games in general. Good DLC is so great that it's practically a steal. It might introduce new characters, stories, gameplay scenarios, interesting mechanics, or myriad other enhancements. inFamous 2 and inFamous: Second Son both had very well done stand alone DLC for these reasons.
Bad DLC, however, is $120 a dozen (The stuff is damned expensive!). Stripped features, game breaking gifts, mundane content that makes you say, "This is just more of the worst." And at its worst, it is just downright broken.
Sometimes DLC is sinful not because it breaks immersion or the bank, but because it is just not very good for the exact same reasons that any full game wouldn't be good. Bad DLC is a catch-all for all the DLC that is technically sinful, but not for reasons that specifically relate to the fact that it is DLC.
So what do you think? Are these 5 sins accurate? Or do you not even consider microtransactions to be DLC? What other sins can you think of?