On tunnning the enemies, that is a point that is very subtle.
I like moslty the enemies too. But some of them feel a bit odd. I did propose only a couple of changes and I think that instead of disregarding the point as no change is needed at all. It should be looked case by case.
For example the umbra, what if instead of reducing its health, overwatch time to fire is reduced so ovelapping cones of fire is made a realiable way of counter them, and Ow is made more reliable in the process? The point is that enemies should have a way to counter them, saying that the claim that they should not have every strenght posible is unreasonable would not fly with me. Im not propossing changes to make the game simply easier for easy sake, but to make it more interesting by making tactical game more meaningful.
For the triton, I think reducing the accuracy on disabling their head, and providing some scanner-like tools does only provide you with some smart tactics to counter them, as they feel unbalanced precisely because currently the game does not have any tool to deal efectively with them.
For explosive artillery, I dont really know what the solution would be. I feel that there is a problem with them. And certainly some places like the final mission feel cheap because of it.
With the Siren, I will grant you that i dont see nerfing them as useful. It is just that it would feel more fair, if the MC ability was more useful to you.
Regarding the abilities, again I think it is a case by case thing. I dont think you would disagree to remove the most OP combinations, like saying RageBurst should remove setealth and ignore MoD. Or saying sneak is currently just too powerful.
The case of rage burst as an ability, is pretty much the only ability that feels bad for me together with MC. Mine is only an opinion, but I dont think making both of these more useful, after removing the OP combinations, would make the game too easy, but instead, more tactical.
With your point of more non lethal abilities, I kind of agree, but there is a delicate balance here, as we already know how disrupting panic loops can be.
What I do not accept is just pointing that there is no need to balance any enemy or any ability, or any ability combination, as meaning they are now as perfect as they can be, and no change is needed at all by definition. Which is disregarding the point entirely without considering what each proposed change is trying to accomplish. Skills that are not useful enough need to be chaged to be more useful. You can disagree on if an ability is useful enough or not, and the same for manageable enemies. But saying no ability needs to be more useful by definition and no enemy should be more manageable by definition does not have sense to me and feels like advocating for difficulty for difficulty sake.