Ok, I get it. You need to progress with the main storyline. It solved my problems. Hoodlums on the street are just too strong if you haven't entered that part of the city in main story?
Same here, but without a fix. Enemies are invincible and I get one shot. Sometimes loading back to an old save fixes it but it reappears nevertheless, game breaking.
Same here, enemies take no damage and kill me in one hit. Tried switching the difficulty, even reinstalled the game. Does not fix it. Really frustrating because I can' advance in the game, missions become impossible.