And then there was ME3's very first DLC. I don't care what Bioware claimed, having a prothean squadmate *was* central to the main plot.
And I actually prefer the game without him. I know that's strange considering he's a Prothean, but geez. He's the most typical "I'm a warrior and I'm built to fight" trope that I've seen in so many other BioWare games. His appearance is too convenient, he's not that interesting and his design is uninspiring.