Especially the challenge tombs provide significant perk unlocks and should be done as soon as possible. Not only will this save time later on, but you also receive bonus XP to make your life easier on Survivor difficulty. It would be beneficial to grab as many collectibles as possible as you play through the game. The main difference to other difficulties is that your health doesn’t regenerate (you must craft med kits to restore health), you take more damage and enemies have increased health.
There are relatively few enemy encounters and you can easily take out most enemies in stealth to avoid open combat. The only hard encounters are at the very end of the game. This is the highest difficulty in the game, but it’s totally doable on the first run. You must beat the game on survivor difficulty for the trophy “Ultimate Survivor”.
