I ended up restarting. The stealth crossbowman was... disappointing, really. Not that it is unviable or anything, but I found it really tedious. The "stealth part" is kind of garbage since enemies are almost never in a situation where you could stealth kill them – they tend to be grouped up, and even if you manage to lure one out of sight through traps and the like, you usually don't have the means to kill him within a single turn (especially on dominating) after which he alarms his friends anyway, so the stealth part becomes kinda moot. Generally, every fight ended up being about kiting enemies well enough while utilizing aimed shot and kneecap, which was doable but not very fun. I guess there's other crossbowman builds that are more fun, but this one wasn't it.
I'm trying a heavy shotgunner this time around and so far it's really good :D The difference compared to crossbowman is night and day. While as crossbowman, I couldn't really tank anything and my damage output was negligible (offset by high mobility and range, I suppose), here I go up close and personal, tank enemy hits like they're nothing, and blast them in the face for massive damage. The only negative is that I'm giving up stealth – it was kinda shitty in combat, but I enjoyed the non-combat part of it (ie. getting into interesting places without triggering hostilities with friendly NPCs). Maybe once I get some of the skills to their max potential, I'll have some points left over to dump into stealth, just for fun? I'll probably end up putting it in crafting instead, but it's a possibility.
On another note, I think I'm in love with pickpocketing. It's such a silly skill, doesn't really help you much in combat aside from some highly situational cases (where the enemy is non-hostile at first so you can steal his meds and ammo), but stealing faction-related oddities you otherwise wouldn't have, along with luxury items is pretty fun, and you have basically infinite health hypos and adrenaline shots, since the friendly commoners and guards always carry some of those.
I couldn't really get crossbows to work without mixing in a few extra things. You're just too weak against armor, and you have little crowd control ability unless you spend your whole life shooting those damn Shock Bolts.
Add a little melee (for Expose Weakness and Dirty Kick) and psi (for the basic 2-turn forcefields and a stun that cannot miss with electrokinesis) and you're good to go. Don't need any OP shit to completely transform the build into something else.
Dirty Kick lets you keep utility slots free for bolts, since you don't need a taser in there, and Expose Weakness can be applied with a jackknife or shiv for like 7 AP or less.
You could get by without using any melee or psi, just by abusing a lot of traps and waiting for a lot of EMP grenade cooldowns, but it was just too tedious for me.
There's also magicians that claim to be able to do 500,000,000 damage vs. industrial bots with one bolt, of course, but such feats are not for mortal men like you or I.