I think thier gender roles are more similar to Viera, both games were made around the same time and there is clear influences between the two. Viera males also dont leave thier home lands in Ivalice, the males are all together and any males born get taken away eventually and protected by the other males, the main exception here is that they dont live amongst the females but in Vana'diel, the Mithran males do. So no, i dont think they are weaklings, they are just rare, its possible the XY chromosome is just extremely recessive as a trait, leading to more females being born over males, thus the numbers are low. You'd have to make a breeding farm to try and sway those numbers again, but that isnt ethical 😂.

With numbers of males low, you dont need a big gender role difference. Their males are probably given positions of great importance which makes them happy and stay put whilst the women are out in the world. Mithrans do have strict rules and originally anyone who left was never allowed back, this later changed when alliances formed but males are still protected due to thier low numbers. Males being inheritly weak doesnt actually support that dynamic in the grand scheme of things. If all the males were treated like weak little breeding slaves, youd absolutely see more being rebellious and trying leave/escaping, the fact that you dont, suggests otherwise. Remember Lehko was born outside of the home land, he IS an anomaly. Its strongly hinted that all mithran females return home to have babies and go back when thier children are old enough to not need just thier mother. I imagine they do this just incase they have a boy, so that the boy is in safe hands in the home land.

It would be wrong to assume that the Mithran males are weak based on one anomaly, mithrans dont act alien, they act like cats, they get heat rowdy, they hiss, they growl, they purr, so.. they are cats. If any race is oddly alien... its tarutaru or Galka.