Remember: thinking that putting 20 soldiers at once against a player without any auto-save points is a challenge - is wrong, it's a bad design
thinking that putting enemies 5 meters behind aiming at your head is challenging - is wrong, it's a bad design once again.
And I'm not talking about stealth missions. I'm talking about missions like that with Tunguska where everyone just jumps on you the moment you kill a dude in Vorkuta to grab his weapon
Anything that forces you to play a save/load game is a bad design