Warblade with Gestalt

[Eldariel]

I would argue that the great merit of gestalt rules is that the additional layer of the character, more multi-dimensional and therefore round and interesting characters can be created to leave the stereotypical clichés of the class system behind .

I'm just going by the examples in Unearthed Arcana (which specifically spell out that if you wanna be a Mystic Theurge, you take Cleric on one side and Wizard on the other without multiclassing - that the system is best suited for representing such concepts). I feel you can generally use multiclassing and ACFs to represent the specific type of character you want already with only one class. Although of course you can reinforce it.

That would be one explanation, but it still doesn't work well with the Archivist - the perfect swordmaster of the Great Library is not really an enthralling concept (okay, actually it is. I give up).

Archivist is just a divine wizard. He doesn't need to be a seeker of knowledge. Maybe he studies all manners of divine spells that can enhance his combat prowess. Indeed, he could be a Paladin of sorts. A Paladin of a god of knowledge, for example. Holy warrior bestown his martial prowess by his divinity to further whatever agendas the god has; in this case, for example, pursuit of knowledge. Combat prowess is certainly needed in the forgotten sources he has to scour.