I lost the crew (with the exception of Doctor Chakwas - didn't know the consequences of not leaving straight away) on my first playthrough but no squadmates, and nobody at all on subsequent playthroughs.
Some of the personnel selections can be a little counter-intuitive at first - the biotic and tech ones are pretty obvious, but when it comes to escorting people back it doesn't matter who you choose as long as they're loyal and when it comes to leading the diversion team it's leadership qualities that count so you need to choose someone used to taking responsibility for others (Garrus, Miranda, I think Jacob works too?). And for holding the line at the end you need to leave your tanks behind (Grunt, Zaeed, Garrus are the three big-ticket ones from memory).
FWIW you should be able to reload prior to the suicide mission, make different choices and ensure a lot more people survive for the game you import to ME3 (if that's what you plan on doing).
Some of the personnel selections can be a little counter-intuitive at first - the biotic and tech ones are pretty obvious, but when it comes to escorting people back it doesn't matter who you choose as long as they're loyal and when it comes to leading the diversion team it's leadership qualities that count so you need to choose someone used to taking responsibility for others (Garrus, Miranda, I think Jacob works too?). And for holding the line at the end you need to leave your tanks behind (Grunt, Zaeed, Garrus are the three big-ticket ones from memory).
FWIW you should be able to reload prior to the suicide mission, make different choices and ensure a lot more people survive for the game you import to ME3 (if that's what you plan on doing).