https://underrail.info/build/?HgcKCAUKAwPCoFUAAMKgwqDCoAAAABnCoMKgWWEAAAAAAAAYAE8mKAEZOcKDFjc-woVJwrXCpEsVO-KfogXioIoD4qKNA-KktgLip6oC378My final SMG-assault rifle build look like this. I have no idea how is gameplay with 18 dexterity, and also I did not play dominating. But hard difficulty definitely not hard enough.
I'm using 7.62 impala with muzzle break (9 shots per burst) and fast reloader and 8.6 assault rifle (green scope and muzzle break). Tactics is simple - in beginning of combat you kill somebody with burst from smg, and then you kill most strongest enemy from assault rifle. After it you can deal 2 more bursts from impala. Totally, 4 bursts per round (9 bullets each), more then enough. If I use adrenaline, I have 1 or 2 additional bursts, depending from ammo in magazine and bonus AP from rapid reloader.
From armor I prefer rathound regalia, because of speed. It allow me to come close and make 4-6 burst and kill all enemies in almost all fights during first round. If there is too much enemies, I try to avoid damage completely by hiding behind walls or columns and making bursts from assault rifle.
Mechanics need for weapons craft
electronics for plasma grenades and shield emitter (high + medium + efficient ~ 1200 shield with protection 300 240 160 39 13)
chemistry for grenades mk4
biology - useless, it was mistake. Think better choise mercantile or persuade or lockpick or hacking
tailoring - useless, rathound regalia best choise for this build
At first I use 8.6 steelcat with barrel compensator and forward grip (+25% burst precision). Not so bad, but not so good even. With such burst precision you can kill enemy on long distance, but you lose your "area" burst damage, because all your bullets come into primary target. In same time, it is not so strong as assault rifle, and distance of burst also not so long. So, I prefer to use smg + assault rifle.
My mistakes -
biology - completely useless on hard (look like biology should be used for melee and psionic builds, not smg), only useful drugs is +critical chance and super health hypo. If you do no mistakes, you did not lose health, and super health hypo just no need. Critical chance is also between 15 and 30% (with googles), it is more then enough. Jumping bean or irongut or aegis also no need, because you should avoid damage completely or avoid it with another stuff, like a gas mask. In same time you have a lot of health hypo, morphine and adrenaline from your enemies.
aimed shot - I chose it on early levels, and still use it in deep caverns, but from my thoughts, you need concentrated fire or quick tinkering.
I make assault rifle with 8.6 caliber instead of 9mm. Think better make 9mm for highest damage.
2 specialisation points in spec ops - I think it work with all grenades, but it work only with 'tactical'