I am not overly bothered by the numbers right now. However, it's looking like those kinds of armies are fielded after a huge unification effort. Either via forming an empire or uniting loads of nomads over a long span of time.

Over in Yorum, I'm currently working on city states having no more than several hundred to one or two thousand men in an army at most. That'll get bigger as we go if they unite, but proportional to the population of each one, it wouldn't make sense for it to be higher.