Or maybe there are several species of them, and we get only to see the tiniest kind of specie in game?
But yeah, I wish to see bigger types of Halla, real badass Harts, and not some type of gazelle-like animals.
From what I recall, weren't the Harts supposed to be Halla mounts instead? I think they changed it to be Harts part of the way through development. That would have been great. Halla are supposed to be dangerous if you treat them like a horse, like, they will legit gore you and feast on your bones if you're a jerk to them.
Ok, maybe not that last part, but they're not the sheepy things represented in DAO/DAI. They really should be bigger to represent their role as mounts and (willing) beasts of burden to pull Aravels.