The Blessed

[MercuryD]

the Dravanians are already been betrayed by the Ishgardians (for whatever reason).

The betrayal was outlined in the DRG job quests. The first Dragoon led a company to the chasm where Ishgard now stands, fought Nidhogg and ripping his eye out at a treasure.

Script:

Before we commence, however, it is only fitting that you are edified regarding our origins. It all began a millennium past, when our forebears resided in the southern plains in humble circumstances.
The Fury, impressed by the spirit of our ancestors, decided it was meet that She make them Her own. So did She appear before Haldrath's sire, a man of courage and integrity named Thordan, and bade him lead Her people to the Promised Land─to what would become the great nation of Ishgard. Their journey brought them to a wide chasm, whereupon Thordan and his people set to building a bridge. It was then that a dark shadow descended upon them─the great wyrm Nidhogg. Heedless of his own safety, Thordan fearlessly charged at the colossal beast. Alas, he was pushed into the chasm by one of his own, a man seduced by the wyrm, and fell to his death.
Taking up his slain sire's lance, Haldrath hurled himself at Nidhogg, even as tears streamed down his face. The confrontation ended when the young man, his hand guided by Halone, landed a mighty thrust that prized out Nidhogg's eye. With a terrible roar of pain, the great wyrm took wing and fled, while jubilation reigned below.

So yeah, this kind of shows that the black-white view we are presented from Ishgard is not completely true.