Addtional coment: If you have a ranged weapon, and if you could see enemies behind doors or grass you can hit them. You can gets this vision for Huntress talent (quite op), Talisman or mind vision pot. The door must be open, and if you can postion yourself out of the enemies sight you will hit suprise attacks every hit.
The best strategy for this challenge is to avoid taking damage for melee enemies. There are some tatics… the most useful is to find a Ring of Speed + ranged weapon augmented for speed attacks. It requires a bit of luck but you can achieve this combination by other ways, like flux enchantment (that one the makes you fastest on water) + ranged weapon or projectile enchanted weapon.
Relics that creates distance between you and enemies are also high valuable (Bracelet, Hourglass, Ethereal Chains [GOAT]) Indeed there many forms to loose enemies, but what you need most is a ranged weapon. The Runer Spec is a bit good for creates distance while on runing stance, and the aditional evasion can save you from unexpected hits (dont abuse it, the evasion will not save you as much as we think)
I respectfully disagree about only using throwing weapons, because at hight levels they dont do much, soon or later you will need a good weapon
Did you filled the waterskin on health well?