Zeromaru X
Arkhosian scholar and coffee lover
Cite the texts than seem inconsistent to you. I am interested in look at these closely.
Well, for instance, in Iomandra the inhabitants of Bael Turath became tieflings to oppose Arkhosia, and was eventually destroyed by the Arkhosians. In the D&D World of 4e, the inhabitants of Bael Turath became tieflings to crush the rebellions and other tribulations that were debilitating their empire way before the Turathi meet the Arkhosians for the first time (see Player's Handbook Races: Tieflings, among other sources).
While in Iomandra Arkhosia survived their meeting with Bael Turath and is still the ruling power of the world, in the D&D World of 4e, Arkhosia and Bael Turath destroyed each other in a series of devastating wars that left dragonborn and tieflings scattered all over the world (see Player's Handbook Races: Dragonborn, Player's Handbook Races: Tieflings, and many other sources).
Just to name a few.