I think the whole "there is a Vex structure inside every celestial body waiting to be activated" thing, the incredible age of the Vex structures on Sol bodies, and the apparent speed at which their structures are built can all easily be attributed to the Vex's time travel capabilities. Any body the Vex terraform must necessarily be terraformed when they first arrive. Then they go back in time to begin the process of terraforming it so it will be finished when they get there. Also, I would argue that the behavior you cite as evidence that the Vex are capable of emotions is only a case of projecting emotions. That they worship the black garden does not necessarily indicate that they experience genuine religious awe related to it, only that they have observed that this behavior has results which are to their benefit. That they flea from the Taken and lure Guardians into the vault of glass to drive them out does not indicate that the Vex fear the Taken or respect the Guardians' power, merely that their simulations show that they cannot eliminate the Taken on their own, and that Guardians can. As a side note, this is probably why the Vex haven't used their time travel capabilities to exterminate humanity at a time when we were too primitive to challenge them - their simulations show that if humans do not exist to eliminate the Taken in the Vault of Glass, the Taken succeed in invading it and using it to erase the Vex from reality.