It doesn't look as though the Eorzean alliance is actually present in Othard and rather that it's just us and the Scions who head there. I assume they'd probably be too busy holding the line over in Ala Mhigo to send forces over.

I also get the impression that the main reason Othard even fell under imperial rule in the first place is that it was divided at the time of the invasion, unlike Eorzea which had established an alliance between the three Grand Companies by the time the Garleans arrived. Hien probably realized that after their failed uprising, which is why he's trying to gain the support of the Xaela tribes (And presumably others, considering that the Kolin are going be getting involved, as well).