In which order should you unlock the mutations? This guide gives you an answer.
Short Tipps and Intro
I made this guide after I've played through the game in the second difficulty level (hard). In this difficulty you have to try to take down most of the enemies in single fights.
In single fights you normally use only silent weapons, but if you are far enough away from other enemies you can use all weapons. Don't forget so save the game, before you use your loud weapons.
Try to create ambushes were you have high crit chances. The silent weapons are first priority for update levels and crit damage upgrades. I did equip the silent weapons as primary weapons.
You can't reskill your mutations, but between fights you can always change the three equipped mutations in the inventory view (press 'i').
You also can change your squad between the fights (press 'k').
With his best skill Hog Rush(2) Bormin can knock down most enemies. This attack doesn't make much noise, you can combine it with silent attacks.
He looks like a tank, but you better try to avoid to tank in this game.
Dux looks like a Sniper, but with Skull Splitter(1), Alpinist(4) or Silent Assassin(5) he is more a crit hitter.
Moth Wings(2) work great in combination with Alpinist(4), if you don't have high locations. With Circuit Breaker(3) he can disable a robot for a short time.
With Tree Hugger(2) Selma can disable enemy movement in an area for a short time. You can use it and fire in the same round.
Later with Alpinist(7) she likes to fire from high positions.
Puppeteer(3) is great against a group of enemeis, because for a short time you can take over one of them. This poor controlled guy takes the bullets for you and you can attack the other enemies with him.
With Silent Assasin(7) he gets a crit bonus while he is hidden.
Farrow has the best stat improvement. You can two times boost her crit possibility with Critical Booster (4,8) and she gets Silent Assassin(2) very early.
With Circuit Breaker(1) she can disable a robot for a short time.