Also, I forgot to mention a correction to the timeline in WOT in the "Errata" section of WOT2, whereas the timeline in WOT stated that the Old Gods started whispering from the Black City in -2800 Ancient. The corrected text verifies that it was still the untainted Golden City "as it had not yet been sullied by the presence of men."
Edit: This confirms for me that the Veil was constructed many years before the Blight reached the Golden City, thus making a dual-purpose scenario unlikely.
Well, I certainly could be wrong. It wouldn't be the first time.
But... I'm not sure WOT is always completely factual, as it is written from within the world, from in-world people's perspectives, right? If it's a Chantry perspective, then they're going to assume that the Magisters are the ones who created the Blight by entering the Golden City, turning it black. That could be true, but it could also be allegorical, or it could be a mistake. Maybe all they did was release the Blight, not create it.
I'm not sure which it is. I'm open to more than one interpretation. But I don't think we can necessarily rule out the idea that the Blight is older than the Magisters entering the Fade physically. The Dwarves have always disputed that claim, insisting that the Blight came from the Deep Roads. So even in-world, we have disagreement on whether the Blight pre-dates Corypheus' & co's attempt to enter the Golden/Black City. Maybe Blight doesn't come from the Black City at all, as the Dwarves claim, and it really does come from the Deep Roads. That's borne out by the "Veilfire in the Deep Roads" codex.
And if the Magisters weren't already Blighted when they entered the Golden City, why would they leave Blighted if the Blight weren't already there? I don't buy "It's the Maker's punishment for their hubris!" argument. But that's just me, I suppose. I'm pretty skeptical of the Chantry and their claims, as a rule.