Now I'm all up for having a few of my guys die and just keep on going, but when my whole squad gets wiped its pretty much game over.
Then I get to this mission, and the Crysallids (however you spell it) are fucking bullshit! Their movement range is huge and they fuck you up so fast! I have restarted the mission 3 times and have gotten wrecked all 3 times! I find it impossible so far because you can't do anything until you spot them and then they get their turn and run right up on you and completely wreck you. I have been doing great in the game so far, no deaths and have been beating the missions a bit easier than I expected I would be. So I just tried the first alien base mission after you build the skeleton key.