The Creators - One of them hunted down her own people for sport
To be fair, she was probably tainted at that point by red lyrium armour (or something akin to it). It's why Mythal had to wrestle her into submission and remove her knowledge of the location of the void.
You mean when they finally comferm it. We already know it happened.
I think it's more likely that the Forgotten Ones (the enemies of the creators) were behind the original taint and that they're linked to the primeval thaig (in which red lyrium existed long prior to the Magisters becoming the first darkspawn) - it's implies in some of the mythology that they (or their ilk) corrupted Andruil. Either way, if the Golden City is proven to be Arlathan (or something that pre-dates the Magisters trespassing), then that'll mean that the Andrastian faith is a lie and that their version of the Maker is false. So it's unlikely (IMO) that we'll ever get conclusive proof of what the Golden City is.
The blight isn't just those five mortal magister's punishment though. It was the sins of Tevinter revisited upon it. There may have only been a handful of people who made the journey but you have to consider what it took to make it even happen. In that sense Tevinter at large (which was the whole of civilisation back then) could easily be considered complicit.
Firstly, Tevinter wasn't the whole of civilisation back then - there were countless tribes in the south independent of the Imperium, the most well known of which (in DA lore) are the Alamarri and their sub-tribes. The dwarves also existed underground and would be the ones to suffer the most from the darkspawn - so if the Chant is correct, large swathes of their civilisation collapsed and most of them suffered a terrible genocide because the Maker wanted to punish a human empire on the surface.
Secondly, if you look at the internal composition of Tevinter, most of its people were serfs and slaves (many of whom were elves forced to serve the Empire that struck the killing blow against their civilisation) who were trapped under an oppressive caste system ruled by a powerful mage elite - they had nothing to do with the sins committed by the magisterium. The blights would punish the people at the bottom more than they would punish the elite (who at least commanded armies and owned fortresses that would offer them some protection) even though these people had nothing to do with the sins of their nigh-invincible masters.
So if the Chant is correct, then the Maker is rather unpleasant. Though if you ask me, the Chant is almost certainly incorrect.