i don't know which squad characters from 2 are DLC but there are too many of them...and they are all fine as characters but like i said, it made no real difference in who you chose because they all basically did the same thing
and it was weird that you use the hovercraft thing quite a few times early on but then it's just forgotten about in the second half of the game...i actually really liked driving the Hammerhead much more than the Mako
one thing i noticed about the trilogy is that it starts as an actual RPG with ME1 and by ME3 it's basically just a third person shooter with some lite RPG elements