#so its plausible that some magister figured out how to create them

[nightingaletrash]

So here's a thought: griffons have a natural, inborn hatred of the Blight that is so overwhelming that they can't be put through the Joining. They will tear themselves apart before they accept it. Even Isseya's modified Joining couldn't make them accept it - the griffons simply became hyper aggressive and would fight to the death, no matter how badly wounded they became. They cared only to kill darkspawn, even at the expense of their riders.

Griffons are also hybrid creatures of cat and bird. You know who loved to create hybrid creatures? Who's whole deal is creating beasts and monsters? You see where I'm going with this.

So what if the griffons were created specifically for the purpose of fighting darkspawn? Like a sort of frontline defense to fight the physical symptom of the Blight, and their rejection of the Taint was a means to ensure that they wouldn't then be corrupted in favour of the Blight.