Ugh, well exactly what the vanguards race for each class. In the beta the Titan vanguard was an awoken, the hunters vanguard was a EXO, and the warlock vanguard was a human. And to me that makes the most sense because the warlocks are like the secret order of the traveler, which originally was helping humans, not the EXO which were built by humans and the awoken who are mysterious. The EXO are hunters because they themselves are part of the wild, they have no beginning and are socially different. The awokens just wanted to help so they made the titans and yea.