They already have good AI. armour and to the last man relies too much on RNG and that's not what they need they need reliability. A damage reduction would give a straight reliable durability buff without loops and hoops and the possibility that they do nothing entirely. Armour adds another dice to them that can still say fuck you if it wants to. Damage reduction is guaranteed.
I dont like dmg reduction on rangers.
I'd rather less units have it, not more.