I belive the vex classifications are like a tree. Starting with a broad group and superheating into smaller units. But I do belive that if given time,(and that's something the vex have a lot of) could very well destroy the city. But the vex collective is not a war machine. Their primary function is construction and terraforming. They only attack when they see something as a threat to the building. That's the reason they attack the cabal. The cabal like to test vex areas and take control of them. Guardians don't have the numbers to accomplish this. This somewhat relates to the vault. Why, of all places, put it next to the light? Because we aren't a threat. The vex new of the taken threat and use us as antibodies to fight off the taken threat. When the taken entered the vault, they released the signal and we went into the vault and defeated the threat. We are no where near a threat to them.

A lot

Very interesting. We will take note of this. I'll let you know when it's classified.

If they really wanted to, probably. ThVex Collective is massive and Galaxy spanning. Thing is, destroying is clearly isn't part of the pattern they pursue in their attempt at an emperor to all outcomes. At least not yet.

The vex aren't only at war with humanity. Really if they wanted to they could just go back in time and turn earth into a machine world, ending humanity before they began. They see a use for humanity and the traveller and wish to understand "the light" rather than destroy it as it has a use to them. Hence they convince you to rid the vault of glass of the taken energy by letting Praedyths messages through because they were unable to fight it themselves.

The Vex are a strong force, but they arn't unthwartable. They do have an advantage in numbers, but that's it. They arn't considerably powerful outside the Vault, and it's unknown if they are capable of inter planetary travel without the use of a portal, none of which exist on Earth. On top of this, they still see us as having a use, an example of this is when they lured us into the Vault with Praedyth's recordings to save them from the Taken. So I doubt that the Vex could or would destroy Humanity on it's own turf.