When the Batarian incident was first brought up in the game, I had no idea what the hell the NPC was talking about and I just rolled with it, not even caring about the consequences of something I didn't remember doing. I knew about Liara being the Shadow Broker, it was obvious that she was on the "Information Dealing Highway" in ME2, so that wasn't a big deal. And James? I really didn't care who he was because I disliked him almost as much as I dislike Garrus from the moment he appeared on screen. I mean, he's an idiot. The only thing I can say about DLC content, is go the route of the Dragon Age: Origins DLC, Awakening. It was completely standalone and set in a different time/location, but still had ties to the original game. This makes it not critical to any sequels, not that it mattered with Dragon Age 2, but more of an expansion on the facts already presented in the original game.