I'm just wondering why is it significant to Sera. The likelihood is is that Sera has never been there before. There are no cities there. There is no reason for her to be there. There has to be more to it.
Alternate theory: The Blight was created by the Ancient Elven Gods as a weapon against the Dread Wolf who rules over the Fade. The Red Lyrium idol that Hawke and co. found was intended as a battery of sorts to power magic (note that Darkspawn emissaries get their magic from the Blight, not the Fade) and to create drones who could fight the Dread Wolf's Spirit friends. It didn't work as intended, so now we have the Blight. There is precedent for Elven Gods screwing up majorly (The Dread Wolf's orb for example.)
What Sera is reacting to are the memories of those who were enslaved and slaughtered in the name of their masters. It would rub her the wrong way.