Mr Jack said:
Makes sense to me; quick wits rather than quick hands. Judging your opponents attack pattern; thinking through your defense; not doing anything stupid.)
I don't see it as having anything to do with judging attacks and thinking through defense. It has everything to do with reaction time and mental chronometry.
In order to reaction to anything, there is a mental aspect to it. Recognizing a threat, identifying stimuli. This is subconcious, and in D&D terms, I can understand how such a purely mental act would be given unto Intelligence. It shows speed of thought. Think of this as the immediate "fight or fligh" response in the mind...or in the case of combat, "dodge or block." Your brain controls the impulse.
To react physically to something, you need physical movement, obviously. Raising the shield, jumping out of the way, what have you. This movement cannot happen before a mental process has occured and the brain has stimulated the muscles into action, or rather, into reaction to the interrepted stimuli. This movement is represented by Dexterity.
Therefore, total reaction time = mental reaction + physical reaction.
Initative, Reflex saves, and Armor Class make sense being dictated by either Intelligence or Dex, and in fact, would make greater sense to have them be adjusted by both. Someone who is exceedingly nimble and graceful might not react quickly to stimuli because of slow mental reaction, even though once the brain processes, he can physically move very quickly.
So a high int wizard can be as good at dodging a fireball or sword strike as a high dex rogue, but not because he quickly calculated the trajetory and knew how to get out of the way. His sharper mind reacted to the threat of the attack even before the rogue did, so he was moving to dodge the attack before the rogue does. The rogue, once he starts to react, physically moves faster. But the time the fireball explodes, they have "caught up" to each other and safely ducked out of the way, the wizard because he moved a second or so before the rogue, and the rogue because he moved with greater speed.