Stuffs that's really just Au Ra Specific and nothing Spoiler happy"The first Ishgardians to encounter Au Ra saw Dravanians. We had fled Garlemald's armies only to come to a land where we were mistaken for another nation's mortal enemy. They bared steel and came to kill us...but we did not die so easily."
The Dark Knight Trainer is in fact Au Ra Xaela, the tribal type that move around and held majority of the Othard territories while the Raen more than likely lived with the Au Ra.. However, he states that he and the initial Dark Knight trainer, Fray, were close, learned what it meant to be.. this happened when he was pretty young, that he was saved. So it was/is in fact possible to be more of an eorzean raised Au Ra.. 

Spoiler
An adult Xaela NPC, mentions him and his family having come to Ishgard while he was a boy and living under the persecution of the Temple Knights. It's impossible to gauge how exactly old he is, but assuming that he is an adult and thus a minimum of say, 20 years old, then we can extrapolate that he and his Xaela family came to Ishgard anywhere from five to ten years ago, if not more. It's a stretch, and it's a unique case to be sure, but it provides evidence that suggests that it was possible that very small numbers of Au Ra came to Eorzea prior to the appearance of the Domans.