That's why it's called "insane".
You could modify DifficultySettings.xml but then you might as well play on "expert"...

Try toggling off ALLOW_TARGET_HEADANDLEG_IFPRONE if it's on, it is kinda a bit wonky if you use NCTH in situations like this, attracting a bit too many hits from what should be pretty inaccurate fire. Other things you can do is increase the penalty when aiming at invisible enemies in CTHconstants.ini (vanilla has something like 50 penalty, SDO for example uses 200 which kinda makes sense, how can you actively aim at something you can't see) and/or modify their CTH bonus at insane difficulty in DifficultySettings.xml.

Or just, you know, don't play on insane it is kinda insane

You could take a look at

CthConstantsAimDifficulty : min -1000.0, max 1000.0
CthConstantsBaseDifficulty : These modifiers are applied based on game difficulty, and only affect the base CTH of ENEMY COMBATANTS. min -1000.0, max 1000.0

in DiffcultySettings.xml and

;------------------------------------------------------------------------------------------------------------------------------
; Enemy CtH bonus
; Theses settings determine percentual multiplier of enemy Chance To Hit with guns or in close combat.
; "0" means <no change>, 100 means the CtH will be doubled every time (so if the enemy would have 30% CtH on the 
; current shot, he has 60% instead).
;------------------------------------------------------------------------------------------------------------------------------

; values represent percentual increase
ADMIN_CTH_BONUS_PERCENT = 0
REGULAR_CTH_BONUS_PERCENT = 0
ELITE_CTH_BONUS_PERCENT = 10

in JA2_options.ini.

Thanks for the info @flugente,
assuming unmidified cth of 50% thats 60%@expert vs 75%@insane, aka a hard to miss improvement of 25%,
either distorted perception or my mercs didnt get shot enough at all.

Regading the cth bonus for admin/regular/elite in ja2Options.ini,
did i get that wrong that this modifier is only linked to type of enemy we encounter instead of difficulty setting?

btw and completely OT, I think the term elite is quite inappropriate.
The real Elite rank requires 6400 kill counts,
assuning that according to C64 calculation a lvl 1 merc or Arulcan rebel would hardly count as a full point,
the so called elites should rank from above average to dangerous at non linear randomness,
appearances of "deadly" ranked enemies get an additional limited
and restrict Elite to unique entities, like 1 or 2 "Terrorists" and definitely Joe,
who should really be "told" that its a bad idea to steal a weapon if he faces a dozen mercs who spawned next to him.

Eh... what? Is there justification on how a soldier shall require 6400 kills to be considered elite, or is this supposed to be some cultural reference I don't get?

Well, I get that it is an improvement, supposedly. But I find that one gets hit more when prone than crouching, either intentionally or by accident, and it also works for the player when attacking enemies who are prone. That's why I find the hit rate when prone too high. At least this is true in the early stages, with lower quality Mercs and shorter ranges. It is the change in the range of 5-15 tiles, mostly 6-10 tiles which is very noticeable (at least to me).

I mean, it all depends on what range is considered easy to hit, and where prone begins to benefit or not. But seriously, I get hit a lot less when crouching than prone. Plus there is a bonus to hit those who are on the ground (as if they are knocked out), and this bonus is large, in effect (have no idea what the value is in the code). I can seriously see how idiots like Raffi, Flo, and numerous other low quality Mercs benefit when shooting at prone enemies. I presumed it might be related to this toggleable feature, so I'm trying it out. Maybe it isn't though.

So, I dunno. Prone has almost no benefit within 10 tiles. In the old system, I think I could see where around 6 tiles or more, prone began to benefit you. But with the new ALLOW_TARGET_HEADANDLEG_IFPRONE I just find that prone is worthless to much longer ranges. In both systems if the attack came from an angle from the side, it was easier to hit the prone target anyway.

I like the CONCEPT, and I like having some ability to target the various parts of the body of a prone target, but realistically, if you are shooting directly at someone prone from similar height, and head on -- you are going to hit the head or the shoulders first, not the legs or the lower torso. I mean sure, we can say that the game has a fudge factor for head-on attacks, in that the target is probably not directly head-on -- but, well you get the idea.

Prone Mercs seem to benefit only from the bracing or "Mounting" feature, or if you later have bipods etc. But defensively being prone doesn't seem to help much to use the terrain or to avoid being hit, like it used to benefit. Makes it hard to see the early stage benefit of being prone, perhaps that is the design.

To put it another way, I think my early stage Mercs benefit significantly from using this toggle for prone effects. This may be because I fight a lot of shorter range battles often in sectors with Militia aid, and I find that in such instances prone targets are getting hit so often it is almost a joke. It almost makes the Militia's crazy antics look sensible with the limited usefulness of being prone.

Of course, I completely forget by now what a Tile's range represents. I used to presume it was 10 meters a tile, but it is probably 2 meters. It seems that during the v1.13 development, the meaning of a tile's range may have been changed.

This post is way longer than I intended. As compared to most pc combat games, you just don't feel prone with this feature anymore. But there have been so many other revisions to v1.13 gameplay over the years, that it's not that clear to single it out. Some of this may be due to the NCTH versus OCTH.

One can adapt either way, but I'm not sure that having ALLOW_TARGET_HEADANDLEG_IFPRONE ON makes the game any harder in the earlier going for the player. It just makes being prone seem a poor choice in the low ranged battles, especially with lots of lesser capability weapons and allies/enemies.

Realism is definitely a factor, why else do we have e.g. nice pics for uncountable weapons,
or to go further, instead of graphical illustration some numbers flickering on screen.