The only thing I would mention is that due to the time traveling nature, it's difficult at best to date the creation (or the source of the creation) of the Vex. It is possible they existed during the arrival of (or, as you suggest, created by) the Traveller. However, it is also possible that they have yet to be created. Once a time traveling race of murderous robots (indeed, robots who wished to write themselves into the very laws of existence/physics themselves) has been established, then it is accurate to say that they have [i]always[/i] existed for all intents and purposes. It's possible that the Vex may even be a creation of humanity, a creation of Rasputin, children of the darkness, or even independent of all known factions. Regardless, it's not established that the vex have any relationship to the Traveller (though it's a very interesting and certainly possible theory).