What is the intended order—play through the story of Mass Effect 3 and then play the From Ashes DLC, or begin the game with the From Ashes DLC from the start?

With the nature of the squad member being such an important and critical plot point, it seems like his presence or absence would affect a large majority of scenes, and I can't imagine that the entire game dialogue is branched based on the DLC, so clearly the writers in most scenes must have either intended the player to have the DLC or not.

For example, am I going to encounter situations where people speculate about the Protheans while the DLC character sits idle without any dialogue written, or, on the other hand, are there really interesting and well-scripted scenarios over the course of the game that are dependent on having the DLC character?