Hello everyone,
I wanted to post an update to this thread before closing it up. Thanks for all of the reports and data that has been shared.
Our WoW and QA teams investigated the reports of FPS drops in Spires of Ascension to determine what was causing this for some systems. The teams were able to confirm what specific art effects were the primary reason for the decreased performance, but unfortunately they were not able to make changes that would help improve the performance while in the dungeon.
What this means is that if you are still only experiencing issues in Spires of Ascension we would recommend tweaking the graphics settings to find out what works best for your system while in the dungeon. Turning down View Distance, Environment Detail, and Ground Clutter should help the most.