Okay then Low, here's my contribution to the Tarkatan discussion
I feel that the Tarkatans are like soldiers on the front lines. They have a strong desire to fight and serve, but I agree that there isn't much to them at all besides that. One way to help flesh them out is to give them motives; by that, I mean give them reasons why they do what they do that makes sense for their character, and also give them history.
Like, for example, you could give them a desire to break out of their nomadic lifestyle in the wastelands of Outworld, and to seek glory and respect from other Outworld races due to their accomplishments under their emperor's rule and their combat abilities
As for the history part, maybe the race could be a result of of Onaga's numerous failed experiments to achieve immortality. Maybe he thought that mixing Outworlder blood with the blood of a demon would help him achieve that (since demons are immortal), but this ended up resulting in the first ever Tarkatans instead. Not seeing the potential in these creations, Onaga instructed Shao Kahn or any other servant of his to cast these experiments off to the wastelands, leaving them for dead. Instead of dying off, they adapted and remained there for milennia
They could also have a leader (whether it be Baraka or anyone else) who has his own ulterior motives in addition to the entire race's goal as a whole