We both tried max settings, everything up; windowed and non-windowed. Ambient Occlusion on/off and Depth of Field on/off. Care to guess what the FPS increase or drop was? No seriously guess? You're probably wrong if you are thinking it increased or decreased.
My FPS remained at 15FPS, 20-23 FPS running around away from the Aether and his remained 20-25 FPS in the starter instance. Odd yeah?
Not really - not unusual at all.
Graphics cards have several subsystems, any one of which can be a bottleneck. In a gross oversimplification, there are three main GPU bottlenecks - geometry processing (how fast it can process polygons), shader complexity (how much computation it can perform to determine how to draw each pixel), and fill rate (how fast it can draw pixels). There are other potential bottlenecks, but I'm trying to keep it simple.
So if a particular subsystem is the bottleneck, reducing settings that affect that subsystem will improve frame rate up to the point where that subsystem is no longer the bottleneck (because pretty much by definition, some part HAS to be the bottleneck). And if a subsystem is not the bottleneck, increasing settings that affect that subsystem will have no effect on frame rate up to the point where that subsystem becomes the bottleneck.
The bulk of the graphics options in FF14 affect shader complexity (even depth of field now - they're using a different DoF technique than they were using in older versions), so if shader complexity is not the bottleneck on your GPU (or if the shaders are coded in such a way that there's not much performance change between having a feature on and having it off)
, increasing those settings won't affect your frame rate.
Things like window size and buffer size affect fill rate, so again, if your GPU isn't bottlenecked by frame rate, increasing those settings won't reduce your frame rate, and conversely, reducing them won't increase your frame rate.
In particular, due to the way the game's options are set up, if your frame rate is limited by the amount of polygons the game throws at your GPU, there's very little you can do to increase performance.