Barbarian Kings theme for Tien Chi sucks. Tien Chi=China
Barbarian Kings=Tien Chi Conquered by Barbarians(mongols) therefore BK Tien Chi= Yuan Dynasty.

Militarly the Yuan dynasty utilized gun powder(It would be out of place in Dom2 though) and siege weaponery of the song dynasty to high amount.

I think barbarian kings should have long range balistas(An long range high strength bow)/cho ku nos infantry(low strength low percision multiple attack xbow, should be used to attack enemy archers/milita/light infantry) Also the calvery of BK should have increased percision, as they where skilled from firering horse back. These improvments would help make BK a not so weak theme.