Of course the Gauls under Vercingetorix were diluted. They had been merrily smashing each other to pieces for the sixty or so years since the Arverni and Allobroges had been defeated. Vercingetorix had to overthrow the leaders of his own tribe to be acclaimed Vercingetorix; the first attcks ade by this "pan-Gallic" confederation was against other Gauls. The Aedui were still allies of the Romans until quite late in the insurrection, the Remi remained so throughout.
And, how did Caesar resolve to defeat the insurrection? He took tow (tribe) by town(tribe), working on breaking the cohesion of his enemy. The very fact that, even when all the tribes were combined, they relied upon guerilla tactics. Does that sound like a strong, powerful, cohesive enemy? It seems that some of the tribes were a little tardy in having their troops turn up - and these would eventually show up, in dribs and drabs, as 'relief' for Alesia. And Alesia was not some clear cut, steamrollering of the Gauls - as the entire campaign was not. Alesia was close to being a catastrophe for Caesar.
Why do you think the Romans bothered with the allied and client Kingdoms to the East? Just for a different way of organising the Empire? It was clearly to interfere with their greater enemies in the area - but equally they were playing the one off against the other; and they made a point of ensuring that they remained intact, independent entities.
Of course the Romans had a powerful military, but to understand their success as simply attributable to that seems wide of the mark. And, Im not sure where you've got the idea that I'm arguing that their dominance is "pure political wit". But the one without the other will gain you nought.
As for the dismissal of the power of the Catuvellauni..... errmmm, how much more "We are conquered" can you get than running to a Roman commander pleading for help in regaining your position, because you've been conquered. I'm not sure what, exactly, the son of the 'King' of the Trinovantes pleading for Caesar's help because Cassivellaunus has killed his father and taken his lands, might imply other than a 'conquering'.
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