Something that remained with me after finishing this DLC are Morrigan's words. In the epilogue Morrigan says, "’Tis said that Corypheus woke after his long slumber and found the world gone awry."
In the final discussion with Solas he says that when he woke up a year before the explosion at the Conclave it was like everyone was Tranquil. He's determined to bring back existence as he remembers it, no matter the cost.
This is very similar to the next line in the initial epilogue narrated by Morrigan, "He fought to bring back those days of magic and shadow, to raise himself as a god, and set things right."
However, I think possibly the most apt parallels is one you can draw with yourself: Your Inquisitor's reaction to In Hushed Whispers is perhaps the most telling.
When your Inquisitor are sent into the future, you see a world in total chaos and misery. At any point, did you think to yourself, "Maybe I should look into this more, and not try to erase this future?"
Erasing this future means destroying anyone who was born. Erasing bad things, of course, but good things, too, even if they seem few. There must be some good things that were present in that world. Perhaps we could have helped the resistance fight the Elder One and take him down instead of erasing the timeline.
However, you and Dorian never stop and consider that you should salvage this world or save it. This world is abhorrent to you. A total catastrophe, and failing abomination. Of course you are going to restore the world you knew. Whatever the flaws of your own world, it is surely better than what you see? Dorian even repeats this to character such as Leliana who replied that this world was real to them regardless of what you say.
There are parallels with Corypheus, yes, but Corypheus, at least, woke to a world that was not too altered. Corypheus lived in a time with the Veil. On the other hand, you entered into and Solas woke to a world that is torn apart from the one both of you respectively knew.
Let us take this further. What if you were sent 20 years in the future? 200? 2000 ? The people kicking around then, all corrupted by Red Lyrium, even the children. The people live as long as 20 or 30. All slaves to Corypheus unless you are magister, a human and a citizen of Tevinter.
Yet they insist, no, their world is fine. It is all good. Though, you know that there was a world that you can return that was so much better. These people, despite being miserable, corrupted slaves, they see value in themselves. Do you erase them anyway? Or do you let this world continue as it goes? That is the world Solas woke up to.
Solas woke up to a world with little magic...A world where Titans slept, Dwarves are sundered, Great Dragons are mere beasts, Elves are weak shadows of themselves...A world where Spirits are feared, where there is massive conflict every 5 to 10 years, where mages are locked up in a tower...A world where there exists philosophies such as the Qun and a world that still practices slavery, especially of Elves...
To Solas, this world must have appeared to be like how our Inquisitors saw the future world in the quest In Hushed Whispers. The Inquisitors proceeds to undo it within an instant whereas Solas at least try to make sense of it.
In Solas' position, I think you know what most of us would choose.The more I think about it, the more I understand where Solas' and Corypheus' are coming from. I cannot hate them. I can dislike them out of a sense of self preservation but I would pity them as well.
The worst part is that the Inquisitor, in game, does what Solas and Corypheus do, albeit on a smaller scale. We traveled to the future, found a world that is abhorrent to us and sought to unmake it. We did so without hesitation, without doubt, without question and without any second thought to the people in that world. In fact, I think only Ameridan was the only person from the past who was okay with the future world.
The reality is that those who are calling for Solas' deaths and those who hate him are hypocrites, doubly so if they did the quest In Hushed Whispers. Upon further reflection, I do not want to kill Solas. I would stop him and only resort to killing him if there is no other choice. For the simple reason the Inquisitor is no different than Solas.
Personally, even I would do what Solas, Corypheus and Inquisitor did if I were put in their position. Without remorse, without hesitation and without fail. I would restore the world to what I knew unless if this alternate world is significantly superior in some way.