Original Problem outlined both here: http://forum.square-enix.com/ffxiv/t...formance-Issue
And here: http://forum.square-enix.com/ffxiv/t...ps-and-Crashes

Both threads have been marked Resolved. However... Neither threads have had any official response or any real progress outside a temporary fix that degrades image quality. There have been multiple calls to both Square, and AMD to fix this issue, and neither party has even responded to the forums. Not even on the first linked one, which has 15 pages did we get a single response.

Anyways...
The Issue
When teleporting to and from an area that is highly populated the game will crash with an unexpected error message. It used to be it would slow down to 1-2 FPS, then crash shortly after.
However now since the 2.4 patch, the crashes are instant.
This mainly can be seen when attempting S ranks, or sometimes when going near the Aetheryte in a populated zone.

This issue mostly seems to affect AMD cards. It happened both on my old HD6770, and my newer R9 270. As you can see in the previous forums I linked there are multiple people experiencing this issue, and still to this day.