Much better to just not have your main squad die, it's not that hard if you don't take silly risks and have built them right. Once you get them in some decent armour and weapons and have a fair build, your soldiers will live unless you do something stupid

Or the game bullshits on you by marching two Sectopods and their accompanying drones, Three Heavy Floaters, A mechtoid and his Acompanying Sectoid Commander on you at once

Fuck you Xcom -.-