And this is why I need to have two mages in my party more often. Thank you. 
Also:
- Vivienne: And now, he uses a demon to create a false Calling to fool the mages.
- Solas: The false Calling was blight magic. The demon merely amplified its power.
HOW DO YOU KNOW THAT, EGGMAN?! HOW?!!!?! *breathes heavily*
The Blight is the single greatest threat to Thedas in existence and he knows stuff about it he's not sharing and its driving me nuts.
I actually never had Vivienne and Solas in the same party. I never used Vivienne until Solas left (I went through the entire base game with Solas, Cass, and Varric, or as I like to call it, Team Change Is Scary.) But I read all the companion banter on the wiki, and someone I follow on Tumblr likes datamining the game to see what she can dig up, so I've seen that banter a few times.
True, okay he didn't drop anyone actually into the Blight, but there must have been some sort of booby trap for them to be thrown back out again. May be it is just there is something about the Fade now because of the Veil that you need the anchor to stay there. Which is why Corypheus was so anxious to get hold of it again because he knows he can't permanently get into the Black City without it. I've felt for a long time that the Golden nature of the city was just an illusion of what it was before the Veil and like Cory says, it was already black when they got there, which broke the illusion, so that is why it appeared black thereafter.
I keep feeling that the Old Gods and the Evanuris are connected in some way. He was just too frantic about stopping the Grey Wardens that he at least knows what the Old Gods are even if they aren't the split soul of the Evanuris. When you throw in Flemeth/Mythal's interest there has to be some sort of connection.
I figured the Golden City was Golden once - I know a popular theory is that the Golden City's what remains of Arlathan. Which, I mean, Arlathan probably was gold, and it did disappear without a trace. Maybe it was always in the Fade, like the Crossroads. Regardless, I do think it was Gold and then corrupted into what it is now, probably by the Blight.
And I get the Old Gods/Evanuris thing, but I still say the Old Gods are more connected to the Forgotten Ones. Seriously, something had to happen to them. And since they had a few mentions in Inquisition, I'm assuming it's not something the devs are trying to sweep under the rug.
Regardless, Solas might be against killing Old Gods simply because it would mean a perpetual Blight on the surface. Awakening seems to suggest that Darkspawn who no longer hear the Call either gain sentience or go mad - naturally, neither would be very good news for any non-Darkspawn.