probably.
as much i know about AO, i think it's done by the hardware itself if the game runs on DX9, so it would enhance the performance if the game would run on DX10/11.

as for the rest, there is a lot of issues, i think it's within the crystal tools engine, but i'm no expert so i can't verify this.
running FFXIV on max settings would probably be possible, tho some of those settings are purely made to make your system bleed.
the worst of all being general drawing quality, which is actually at max if you use it at 8 (standart), setting it higher just means that the quality will be multiplied with your current desktop resolution.
running at 8 is your exact resolution, running at 9 multiplies it with x1.5 and 10 multiplies even to x2.0, so it's like running the game at x2 of your screen resolution.

but i think those problems will slowly be resolved as have others since the release.
at the release the game performed very badly on my current system, but since then it has improved with every patch and driver update.