There are sub-optimal builds, but thats probably more a balance issue than anything else, as new feats have been added for various weapon types etc. Crossbows are generally weak, and their old strengths (versatility and different abilities via special bolt) are now more easily accessible via guns and throwing. However, this could change before release if Styg adds in new feats for crossbows or updates the ones in place. From my own playthroughs, my thoughts are that crossbows could be fixed by tweaking ap costs - these are very high at the moment for quite mediocre damage output.
However, a build based around crossbows as the primary weapon is going to be difficult (but not impossible - it would synergise quite nicely with traps and throwing, and I could quite easily see a decent stealth/crossbows/traps/throwing/crafting type survivalist build).
Pure unarmed (as opposed to fist weapons) is probably also a bit weak these days; force emissions was changed to doubly nerf pure unarmed - the small range it previously offered was lost, and fist weapons were given access too. Probably the final nail in the coffin is that the latest hotfix has put a floor of 4ap on attacks, meaning you can easily reach that with fist weapons too. I'm not sure that I'd class this as a trap build however, because there is nothing stopping an unarmed guy using combat gloves.
Its arguable that the biggest 'traps' skillwise are in fact hacking and lockpicking, along with pickpocketing, mercantile and possibly persuasion. With oddity based experience, and an economy that provides lots of cash once you're past the initial few hours of the game, the first four skills are worthless whilst so far I've not seen much use for persuasion (though I'm deliberately stopping my experimental playthroughs just after I get the drill parts, so its possible that that skill is used more in the later parts of the game).
What the changes (at least from when I last played this game over a year ago) have done is make build choices more defined; feats in particular have been added or modified, generally making it harder to qualify for them. This can lock out versatility as you have to balance stat distribution much more ruthlessly now. Its still quite easy to make a single-focus character such as a stealthy sniper type, or heavy armor AR specialist say, but if you want to add in good Psi skills (say) you have to look very carefully at the eventual feat loadout you'd like, and work backwards to your initial stat requirements.
But don't get me wrong - I like this, as tinkering with build ideas is half the fun (if not more) of a game like this, and its why I've racked up so many hours in the game. You end up playing with different ideas to see what works effectively and what doesn't.
Its definitely also much easier now than it used to be (or perhaps the difficulty curve starts to ramp up a bit later) - my latest builds have strolled through the junkyard, which was often a place where build deficiencies become glaringly obvious.
For anyone that cares, my current thought on most min-maxed build is a AR/Sniper with strong Psi skills (i.e. all 3 max'd) - this can be done either as heavy armor or tactical vest versions, with the latter investing in stealth and so making skill spending trickier. AR gives you high short range damage via bursts, sniper gives you long range and high armor penetration, Psi gives you cc and 'free' damage for routine encounters via regenerating psi.
Light armor version: Str 06 +1 @04; Dex 04; Agi 04 +1 @24; Con 04 +1 @20; Per 06 +2 @08,12; Wil 09 +1 @16; Int 07. Feats: Opportunist, Aimed shot (Per 6, Guns 10), Psychosis, Gun Nut (Int 7, Mechanics 15), Premeditation (Psi40), Ambush (Per 6, Stealth 40), Full auto (Str 7, Guns 40), Concentrated fire (Per 8, Guns 60), Commando (Guns 80), Locus of Control (Wil 10, TC75), Ballistics (Int 6, Tailoring 35), Power Management (Int 7, Electronics 15), Expertise, Pyromaniac. Skills - max guns, psi, stealth. Buy throwing to 40-50ish for utility, crafting skills as necessary to craft a psi-beetle based tactical vest, max out mech and elec as much as possible to craft better guns and devices.
Heavy armor version cuts dex and agi to 3, adds 1 to str (for 8 total) and 2 to con (for 7 total), drops ambush and possibly ballistics and takes juggernaut feat and possibly recklessness (as the extra hp and armor allows for the extra crit here or there).
Edited to fix a couple of typos.
