I'm really enjoying this setup:

Custom Asmodeus Paladin - Oathbreaker (does a bit of everything)
Karlach Barbarian - Wildheart (Frontline)
Shadowheart Cleric - Trickery Domain (Support)
Astarion Rogue - Thief (Stealth Archer)

My typical strategy is for Karlach and my character to storm in and do a bunch of damage up close, while Astarion sneaks around for stealth attacks, and Shadowheart handles the buffs and whatnot (aided by my character, who also has Eldritch Blast).

Working really well so far! Plus, my character can speak with the dead and handle speech checks, Karlach can speak to animals, Astarion can pick locks, and Shadowheart helps out with rolls as well (I can't remember what that is called at the moment). So lots of bases are covered outside of combat!