So I finally fished the the Deep Caverns.
Impressions regarding this thread topic:
1) CAU armor is NOT the only useful armor as some have suggested. I am glad I took mine two Galvanic Overcoats (one with anti-rifle vests and one light for stealth). They were great against Coil Spiders and psionic Thorchlings. And since I had Juggernaut feat, anti-file one gave me extra 25% health.
Also, I am thinking it was a mistake I did not took my stashed metal armor from Underrail, since it would have been really useful in Arke Plant. Luckily, warehouse was full of metal armors to choose, in a pinch.
Similarly, anti-thermic armor would have been useful against industrial bots and kamikaze bots in the vents. Sure there was anti-fire suit to find inside, but it removed -10AP and have no mechanic resistance against bot heavy melee punches (which are not animated by the way). At the end I did find decent leather armor with 25% mechanic and 50%/20 Heat resistance, inside the Plant, so that is something. Metal armor with both energy and heat resistance was not an option due to ST9 requirement (had ST 8 only).
At the end, I did got to Arke Plant slightly unprepared, so I mostly used by Galvanic Overcoat and CAU armor against poisons.
Also did skip IRIS boss fight, so my shields did most of the work agains small skirmishes. Not sure what kind of armor would be best for that fight. Probably metal?
2) Hypos, bandages where abundant. More looted then used up.
3) Did not spend all of my 7.56mm AP ammo, so there was no need to use my fallback SMG with 9mm AP ammo.
Still, I did try to minimize use of AP ammo, for only when it is really required. For example, even if enemy has 50% mechanic resistance, it would be killed with regular ammo, if it is not hard to do so. Primary targets for AP ammo were those snails and industrial bots (and Tchort of course). I also tried to use Phaser with Aimed shot in Arke power plan. It would either kill crawlers in one shot or with one Phaser shot, plus one SMG shot that I could use in same round. Sure, two SMG burst would be more effective, but this tactic was mostly used to save some ammo.
4) Faceless were not hostile, so Warehouse became my base of operation, where all useful loot was gathered from other places.
Additionally, DC has not enough merchants to sell all loot, but it is still useful to loot everything and move it to single container, since this way you make sure not to miss any plot items you need to find (you see all containers looted, and you know area is cleared out).
5) And what got of the Tchort, you ask. Well I killed him twice. Once accidentally when I got to the ladder unprepared. I just used full force of my sniper build. Snipe then couple of aimed shots. Actually, it was not accident. In first accident try I was dead. Next was right after it when I got to ladder when already in the stealth.
After that I dot fully prepared with solving mutagen puzzle and taking out 3 mutagen containers with explosives and one with SMG. And truth to be told, it does not seem this made battle much easier, since it spawned a lot of Tchortlings, including couple of psions.