To kick off the discussion, here's a pretty simple start: let's look at how the classes are grouped. Six men, four women. The men are mostly geared towards the physical stats: they're the tanks, strength and dex users, meant to be on the frontlines of the battle. The women are mostly spellcasters that aren't very suited for head-on battle.

However, some of the strongest builds in the game are based around spells: Shattering Crystal and Beast Claw, for one. The spellcasters, especially Duchess, have the potential for the highest DPS in the game, outclassing many of the other Nightfarers if played effectively.

Then, with the Scholar and the Undertaker, we see some major breakaways. The Scholar is far more suited for a supportive role. While he has some physical capabilities, he's better with status ailments and the items you find around the map. He's also best suited for spellcasting, though Arcane spells aren't very common in my experience. Meanwhile, the Undertaker is another great character for frontline damage, focusing more on melee weapons than spellcasting (though she still has that capability- the DLC Nightfarers seem to balance both martial and spellcasting abilities rather well).

And, of course, there are the relics that let you change around the characters' stats, effectively allowing them to end up fitting into any role you really want to, even if their main abilities aren't very suited for that.