Vary the AI across difficulties, gangs, ranks, specializations, morale, danger, time and based on how the player is faring -> a great idea
Obviously cripple AI behavior [on higher difficulties] -> not good
Why people play higher difficulties? I don't know, don't have any solid answer. But if I would guess they want some challenge to overcome. Not many things will leave a sour taste in the mouth more than after the hard earned victory finding out that I'm looting 10 medpacks, none of them used in the battle...
But yeah, AI is there to stoke our egos anyway, it's just the obvious part - that it's forbidden to use the same tools as we - about which I would be rather cautious. So varying weights of actions across difficulties and danger levels might result fine, but turning off completely not so sure. There isn't anything to indicate you're making such restrictions though. So I'm just musing aloud.
If I may a guess: it's not the healing on its own what makes Nomad frustrated, but that the battles take too long. Am I right?