Well, that would be because I sort of disagree with Moonpaw.

The default standard NPC mob is equal to the party size. So while the combatant classes are going to be the major players in combat, even a combat-secondary class is more than a match for a standard npc unless they deliberately eschewed any options that gave them combat ability.
Right, but combat isn't their class role. I was concentrating on that, I missed the non-class character aspect because it felt separate, not part of the equation.
It sounds like the goal was for each archetype to be unchallengeable in their own area of specialty, while others could contribute meaningfully but to a lesser extent in most areas.
Well a lot of the classes have overlapping areas: by the roles mentioned at the beginning of the class section only two (Explorer and Keeper) have only one role (not counting the Wildcard role in this equation). The combatant discrepancy comes because only Courtier, Explorer, and Keeper don't have at least a secondary role that could be about fighting.
But other classes -- by class features -- aren't oriented around being combatants or being primary combatants:
* The Assassin mostly has abilities for being "sneaky" in social situation.
* The Burglar is mostly avoidance.
* The Captain's features are mostly all buffs for others.
* The Sage is mostly about helping others achieve things whether by skill check assistance or a vitality-restoring speech or by luck.
So you end up with 5 classes that are (or at least could be in the case of Mage and Priest) primary combatants: Mage, Priest, Lancer, Scout, Soldier. The breakdown more becomes:
* Low combat potential: Courtier, Explorer, Keeper.
* Medium combat potential: Assassin, Burglar, Captain, Sage.
* High combat potential: Lancer, Scout, Soldier.
* Wildcards: Mage, Priest.
So there's really a spectrum of combat capability rather than a duality.
EDIT: Perhaps if you want to take a look at what Psion is talking about you can check out the
free, pre-built Level 3 sample characters.