ok, i have to put my dragon age: dreadwolf theories down somewhere for posterity, so my thoughts on dreadwolf and the origin of the blight:
what if dreadwolf is the blight?
theory + supporting evidence:
the dreadwolf title announce page says that "dreadwolf" is solas' namesake
solas himself says that "the dread wolf" is a misnomer
solas leading the dreadwolf into the fade, potentially as a weapon to use against the evanuris. i take the former picture as his own interpretation of his actions (freeing, leading, liberating) and the latter as the potential truth (the wolf is a dangerous weapon). it also looks tainted
solas could have tricked the evanuris into believing the blight made them stronger, when it only made them mad and evil.
this would explain why he is the dread wolf - named after the dreadwolf, the trick he pulled to defeat the evanuris, the cloak in which he wrapped himself.
the evanuris are locked away; each god a key in the black city, protecting thedas from the blight. he has to create the veil to do this. binding them into the fade itself prevents anyone from reaching them - or so he thinks.
the black city is breached; the magisters let the blight into thedas; gradually, the gods find their way into the archdemons, and the death of each one is another chain falling off the black city. when all are killed, the blight's full force will invade the fade and thedas
ever since, it has been growing more powerful - infecting even lyrium, now. desperate to stop it, solas must turn around and face the weapon he used, stand between it and the world. there are two gods that remain (the ones we see in da4 concept art). when they are dead, the blight will ravage everything in its path.
this would explain why he loathes the wardens, why he tells them they're messing with things they can't understand. they're killing his keys. not that they have any choice - but they are, and it will eventually unleash the true power of the blight.