Guards! Guards! gets my vote for funniest book ever written. But I don't think Sam has a class; he isn't an adventurer. He's just a guard NPC with higher-than-average intelligence and charisma (or is that krisma?).
The problem with this argument is that it applies to EVERY literary example. You comment that rogues, for example, have a "signature ability". I would assume that means sneak attack. Show me a literary example please of a rogue whose signature ability is stabbing people from behind or by surprise. After all, Bilbo certainly isn't a rogue by that standard. He's just a peasant. No D&D class at all.
See, this is why I say that the argument for archetype is pointless. You can make the identical argument about EVERY single example that gets brought up. Vimes isn't even a fighter? Seriously?
Ah, crap, now I understand the confusion. I said Cutter and I meant Croaker. Sorry, my total bad. It's been a while since I read the books and I got the names mixed up.
But, Croaker, Miles and Vimes all share similar roles - they are commanders, even if they aren't in command. They inspire those around them to do things they normally wouldn't do. Which is exactly what a Warlord should be doing.
It's a pointless argument at the end of the day. D&D classes do not represent literary archetypes. They don't. They are completely self-referential game artifacts that only exist within the bounds of the game itself. Trying to apply them outside of the game will never, ever line up 1:1.
So, yes, this is a totally thin argument. Since none of the other classes have any literary archetypes that line up any better than a warlord does, then, well, you can't really argue against a warlord based on literary archetypes.