Well and from where? either you trying bull me or i missed that. Besides in what they belive doesn't matter blight still was caused by magisters...
From the Codex if you play as a Dwarf:
The surfacers claim that the first darkspawn fell from heaven. They spin tales of magic and sin. But the Children of the Stone know better. The darkspawn rose up out of the earth. For it was in the Deep Roads they first appeared. Creatures in our own likeness, armed and armored, but with no more intelligence than tezpadam, bestial and savage.
At first they were few, easily hunted and slain by our warriors. But in the recesses of the Deep Roads, they grew in numbers and in courage. Our distant thaigs came under attack, and now it was the army, not a few warriors, being sent to deal with the creatures. Victories still came easily, though, and we thought the threat would soon be over.
We were wrong.
--As told by Shaper Czibor.
From the wiki:
The dwarves give little credit to Chantry beliefs, but they themselves have no known origin story for the darkspawn. As far as the dwarves are concerned, the darkspawn simply appeared. The darkspawn hordes that invaded the Deep Roads ended up crippling the dwarven empire, leaving only Orzammar and Kal-Sharok, the latter of which was completely isolated from the outside world until recently.