The shot will always fall in the reticle. If the reticle is NOT 100% on the target, it might miss the target. But if the reticle is completely on the target, the shot will hit 100% of the time. In other words, within the reticle, there’s some randomness, of course. But there’s no randomness in terms of whether you’ll hit what the reticle is touching. It’s got nothing to do with difficultly level and everything to do with the game’s design.
As for damage, it’s 100% deterministic. It’s never a range of values.
I actually didn’t take my own advice in Phoenix Point. I’m playing at the default difficulty.
-Tom