So, this is a guide for how I won nightmare on Orc: Embers of rage with a shooting adventurer. I'm a reasonably bad player, barely able to beat normal on the main campaign, and hadn't at the time actually beat Orc: Embers of rage at all. Also, I played this on a laptop with a cracked screen and without a numpad. For the most part, I only moved in straight directions and tried to avoid using the trackpad.
Race: Whitehoof (needed)
Class: Adventurer (needed)
The build resolves around shooting stuff with your 3 guns using the 'shoot' button. Occasionally you need to reposition yourself using the instant-move from chronomancy, however the wast majority of the time your shields will be enough. I put mostly everything else on autocast so it's less work. I also use 'auto-accept current target' so I literally only have to hit '1' to fire. On the rare occasions I had to target something else than the nearest creature I moused over it to change target before firing.
At the start, head straight back to orc town to buy the 'shoot talent' (yup, you don't start with it). Buy physics/chemistry and 'combat training' as soon as possible also. Head to yeti lair for the first level ups. Don't forget to visit Kaltor after both Vaparous Emporium and the docks to look for general gear and bullets, aswell as t4+ gems for telekinetic wielding early game. The ice bullets are really good, if you can find.
For added lazyness, put 'Rune: heat beam' at autocast when enemy visible. Same for 'beyond the flesh' and 'Kinetic Shield'. 'Weapon folding' should be on autocast 'when no enemy visible'
1. Shield (on autocast when enemy adjacant)
2. Steam Reactor
3. Medical implant
4. Medical implant
5. At level 10: Shield (also on autocast when enemy adjacant as it won't cast if there is other shield active)
Dexterity > Cunning > Constitution (feel free to mix up it during levelling)
Talent trees and skill points (roughly in order of importance)
Generics: Chronomancy: Spacetime weaving (1+,0,0,0)
Instant move for initial 5 range. Teleport next to a corner and walk around to disappear from view when in difficult situations. It's just ****** awesome. I never missed having a bigger range.
Generics: Race / Whitehooves (5, 4+,0+,0+):
This is what makes this build. The +10 to strength and +10 magic from the first talent along with a telekinetically wielded gem solves all your stat dependencies. The extra movement is golden when you're moving backwards to reload bullets and the flat damage reduction is awesome (especially for those horrible times when you get hit by a ton of stuff when rounding a corner)
Generics: Corruption / Demonic strength (1, 1+, 4, 3+)
Second talent is a great 'crap-i-need-healing-now' early game. Extra damage from third talent is massive. The damage reduction from the final talent is huge, but with the talent maxed in endgame I started having trouble with it draining all my vim (and thus losing the benefit of the third talent). On my attempts at insane I switched out this for Spells / Aegis (3+,5,0,0). For nightmare I'd rather keep this though.
Generics: Technique / Combat training (5,1/5,0+,0,0): buy in town
If you manage to buy a good lategame light armour at Kaltos, consider using the points here for tinkering instead. If playing at insane instead of nightmare, strongly consider putting points in accuracy. Vaults and some random bosses are really difficult without pumping accuracy.
Generics: Steamtech / Physics (1+,0+,0+,0+): buy in town
Generics: Steamtech / Chemistry (2+,0+,0+,0+): buy in town
Use as you want depending on what you find and need at the moment. You are basically looking for passive bonuses and mostly everything else is useless. I found explosive shell to be my favourite shell late game. As you're covered by shields most the time, I used second skin as the body-tinker for the regen. For Weapon modifiers I switched around, but the armour penetration + crit-rate remained a good choice throughout.
Class: Steamtech / Gunner training (5,0+,0,0):
Get dexterity to 18 as soon as possible and buy the first talent point here. Before that, you will only be able to fire the mainhand gun! Max as soon as possible. Double shot is nice enough once you have spare points and more than enough steam.
Class: Chronomancy / Temporal Combat (5,1+,5,0)
First talent gives a much needed early game damage boost and a good chunk of extra speed. Max it early. Second talent is nice to fire off if disarmed or otherwise lacking in usefull things to do. Third talent is a good for 'making random stuff happen automatically when I shoot at enemies'.
Class: Psionic / Absorption (3+,3+,0,0)
When starting put one point there when you start to get telekinetic slot. Wield an additional gun here, but swap out for gems at level up if needed (for additional strength/magic). If times are though and you actually need to flee, remember that you can deactivate these talents for a damage shield after talent point 3 (I used this only once though).
Class: Spells / Temporal (1,5,1,5)
Time shield is awesome and gives a nice regen after it breaks. I put this on autocast 'when enemies in sight' so it's used as often as possible. Not the most efficent use, but it's good enough. The global speed buff from the final talent is awesome. Don't starting putting points here until your mana is at 300 (don't worry about it, it will happen by itself around the right time)
Your final category point should be used on an inscription
Class : Inscription (at level 10)
Your level 10 category point should also be used on an inscription (you still have more than enough good places for classpoints)
Class: Steam / Furnace (at level 20) (5,5,1+,1+)
At this point you should have found bigger generators, so steam should be no problem. First talent is awesome physical/fire damage and penetration increase. Second talent gives massive flat damagereduction that fades fairly fast with repeat use. Third and fourth talent is automatic reset when it 10 charges. I never found the damage to be noteworthy, however automatic venting is nice. Chronomancy / Stasis is a worthy contender here for the addional time shield. I use this on insane.
Class: I don't know (at level 36)
I got poison here on my first playthrough, thinking that a bit of random poison spread would be a nice addition. However, as it turns out, guns don't work with poison. 'Corruption / Shadow Flame' is awesome if you have the teleporting light which spreads fearfire (I forgot the name). I guess 'steamteach: Bullet Mastery' for the third talent 'Percussive Bullets' could be usefull for the knockback effect also. It didn't really matter, as I was winning easily anyways.
Yeti rewards: not too important. I grabbed 3xchant of fortitude and resolve.
Gear: Bullets are first priority. Range on your guns is really important, and should be preferred over damage most of the time. Saves and immunities are first priority on general gear, as avoiding status effects is first priority. Generally just use the best overall equipment you find though. 'Fearfire' cloak is a pretty nice, and often for sale at Kaltos.