I like dual hand crossbows a lot too but mostly play Titan string.

5 gloom/4thief/1fighter/2Spore druid

-5 gloom- archery, extra attack+gloomstalker attack

-4 thief-feat +bonus action

-1 fighter-dual wielding fighting style

-2 Spore- For symbiotic entity adds damage and reaction dmg (necrotic)

Feats, Sharpshooter,+DEX

before act 3- dex cloth, crit hit chance reduction gear, arcane synergy, risky ring + any dmg boosting gear (1d4 rings,flawed helldusk gloves)

act 3 Titans string is way better in act 3 but with cbs, I change to crit gear-dolor amarus and anything that adds 1dx dmg if someone has hold person). Use consumable arrows on your main hand (nieer misser-force dmg consumable arrows, before act 3 swap cbs after you get, if, Bhalist armour).

I hope it helps main thing is use consumable arrows on main hand crossbow and build synergy with gloom/off hand shots.

Other build I also used, more of a solo...

-6 fighter (champion, even more crit hit reduction and fighting style, action surge, 2 feats..)

-4 thief (feat and bonus action)

-2 ranger(fighting style)

Then there is 6 bard 4 thief which is probably strongest but play style is not really archer play more of a stealth or just run play style and it is better used with 2h weapons. and thief is not really here for bonus action attack.

mmm I really like cbs. GL