Swaenhylt was the focus of a quest added in Patch 1.17 of the original FFXIV:
http://chrysaliswiki.com/quests:ffxi...ing-confession
He was absolutely
obsessed with Azeyma, and sent you on a journey around Eorzea to extract confessions and penance from anyone who hadn't been living a virtuous enough life to satisfy their vows of worship for Azeyma.
I feel like if
anyone in Eorzea would want to know about the events of Aglaia, Swaenhylt has to be pretty high up on that list.
And yes, he survived the Seventh Calamity.
He's even standing around in Camp Drybone blaming people's lack of faith in Azeyma as being the cause of the Seventh Umbral Era:
https://ffxiv.gamerescape.com/wiki/Swaenhylt#Details
And he has a brief role in the early 2.00 MSQ, where he tries to proselytize to you about worshiping Azeyma.