FPS drops momentarily while inside instances.

[Merkaris]

Could be antivirus scanning files that are attempting to be read and loaded by FFXIV. How fast is your hard drive? You should keep the Windows task manager open and focused to see what process is consuming those resources during that period of activity.

GeForce GTX 580M
Intel Core i7-2670QM CPU @ 2.20GHz
16.00 GB RAM (15.95 usable)

Is that what you needed to see?
Also, my anti-virus isn't scanning during my game. That's not the problem.

Edit!-
Also, I've checked it during the game and while it was lagging. Aside from FFXIV, the second/third highest processes (in terms of memory) have been system-necessary things like explorer.exe