It does seem like about 90% of the combinations do make a permanently angry Male Au Ra but it is possible to make one without the resting bitch face.

Also I noticed something interesting in the lore of the Raen Au Ra

"Families of the warrior class (and generally the ruling class) are the only people “allowed” surnames in Doma..." From here

which seems to suggest that the Raen are actually matriarchal, and that the idea behind the gender differences between the Au Ra is that the women are the brains while the men are the brawn.

As for the complaints about the womens stature and look then I say the same thing as other posters have, SE is just conforming to what people like prefer. Just look at how common Lalas and Fem Miqo'te are compared to how rare Highlanders and Roe are in general. The fan base favors the small "cutesy" look over the rough "cool" look.