Crossbows kinda need some mixing, most fun I had in a crossbow build was when I used a Jackknife to apply Exposed Weakness for just 8 AP to deal with robots, Dirty Kick to stun (need quick slots for special bolts, not taser), and just enough Psychokinesis for Forcefields which lets you do all sorts of fun stuff to plug holes in a weaker build or after a mistake.
There's some insane combos you can do, like against a Deep Worm you can use Forcefield to barricade yourself against the wall and force him to act after you, then do a Jackknife Expose Weakness to make sure your Dirty Kick gets through and doesn't get absorbed, then a Dirty Kick for a stun and +25% opportunism damage, then an Aimed Shot from your crossbow for a guaranteed kill. All without wasting Adrenaline or anything else.
However even with all these tricks you still have massive trouble against the final boss if you didn't do the mutagen puzzle, you don't have enough burst damage once your abilities go on cooldown.
Only a steady flow of elemental bolt crits will give you enough burst damage to kill the boss in time, since you basically need to emulate a high-powered SMG as well as you can. It's not too bad but it could be a problem if you aren't equipped for it. (Cyclon with crit chance scope and crit goggles)
Btw random factoid but bear traps work on most robots, even though you wouldn't expect it, even on industrial robots, so Deadly Snares might have some use after all.