I beat the game. The final mission was pretty rough, without going into spoilers.
Of the final team, only two made it out, Bridgette "Omen" Gallagher the Psion and Penny "Smokey" McDonald the Grenadier. It occurs to me that this is unfair. Bridgette and Penny were randos that I didn't really care much about, secondary people who came onto the force very late or to replace fallen veterans. Bridgette replaced Missy Elliott who died to a Chryssalid (it wasn't worth it) and Penny was an HQ recruit cause I couldn't maintain veteran heavies.
The casualties were hard one of those Game of Thrones style roster wipeouts. Raiden died, his antics finally caught up with him but he took a ton of guys with him. Sparks, the specialist, got blasted by a Gatekeeper in like the second room. Bullseye Jeong, the smoothest operator on the team, got taken out by a MEC trooper. My latecoming heavy weapons guy, "Tickle," got mind controlled and Bridgette had to put him down with a Soulfire before he chewed us all up.
Aside from the only survivors being nobodies, it was a pretty exciting finale. Things were down to the wire and if certain abilities hadn't gone off cooldown the exact turn they did we wouldn't have been able to win.