Shadowcaster is overall my favorite class and they make for good skirmishers. They can do a lot of damage at range or in melee, while their varied skillset and expertise makes them useful in exploring. There doesn't seem to be any enchanted shortswords or raperis except Whiteburn (which I've never been able to craft) and Doomblade Rapier (which doesn't count as magical for overcoming damage resistance), so they are mostly limited to +1 daggers for melee though.
Along with them, I like to have at least a Wizard and a Cleric, since they are the only full casters in the game right now. Of the Wizard subclasses, I like the Greenmage the most. +2 to accuracy and dex mod to damage makes it a preferable alternative to Firebolt levels 1-4 and still a viable option at levels 5-6, though Potent Cantrip ultimately makes Shadow Dagger perferable due to guaranteed damage. Getting light armor and Ranger spells is convenient. I don't find Loremaster or Shock Arcanist to be particularly interesting or to bring anything I feel I need to a fight that the baseline Wizard doesn't. Shock Arcanist is boring and functional, but Loremaster seriously could benefit from a rebalancing to make it more than a meme. Same goes for the Insight Domain for Cleric. Once Sorcerer becomes available, I'll see if they have more interesting variants than Wizard.
On the Cleric side, I've yet to find any one archetype I prefer, but Sun Domain coupled with Potent Cantrip makes for a very fun Sacred Flame spam once it hits level five. Oblivion Domain has more useful class features though and I'd say Battle Domain probably makes for the strongest damage caster, with Magic Missile, Flaming Sphere and Fireball added to their spell list. Elemental Domain also makes for useful spellcasters, but with more focus on utility than Battle has.
The last slot goes to someone who can stack AC, usually a martial class. Spellblades, Paladins and Hunter Rangers are solid options, but a Sellsword Shadowcaster Rogue or Life Domain Cleric can make good frontliners too. Spellblades make particularly good dex based martials, because there is a serious lack of magical finesse weapons apart from daggers. Their level 3 ability makes every weapon bypass resistance to non-magical weapons, which is useful for stuff like the Doomblade Rapier.
This is more of a generalized setup than a specific party and it kinda showcases part of the reason why I wish we'd have gotten Druid instead of Ranger. We will have both d6 Arcane casters and a multitude of martial characters, but only one divine caster? A shame, really.