In my first playthrough, I got Mordin and Thane killed in the not-so-Suicidal mission, but I so want to have them back in ME3. In fact, I think I'll got back through ME2 again and have Jack, Grunt, Jacob, Samara, Tali and Garrus my "dead squadmates". I can see Jack, Grunt and Jacob being completely irrelevant to the story, so no qualms there. Samara was a cool character, but likewise, she's probably not that important to ME3. Tali and Garrus are more there to troll myself, since I want to have people dead (well, not Mordin anyway) to make up for me being an idiot in the suicide mission, but I want them to be important characters that people will hate to lose. I like Garrus more than Tali, but Garrus seems like he's going to be a part of the side story, whereas Tali is most certainly going to be part of the main plot arc if she survives. Depends on whether or not Mordin and Thane are confirmed party members or not I guess.
I also didn't pick Miranda because the whole Cerberus thing seems pretty important. I still don't like her very much, but Miranda, The Illusive Man and hopefully Miranda's Father should be a big part of the story.