Poor performance from a high-end build?

[demacy]

Build:
MOBO: z77 fatal1ty performance
GPU: GeForce GTX 670
CPU: i5-3570k @ 3.4ghz
RAM: 8GB DDR3 Corsair Vengeance
PSU: TX-Series 750W Corsair
OS: Windows 7 64-bit Home Edition
My temperatures are fine when running as well. My CPU stays at about 40C and my GPU runs at about 50C.

OP your system build is just fine, it's high end and the parts are well matched, the bad performance you're getting has to be software, e.g. when is the last time you updated the drivers for your bios, gpu etc. and or wiped your HDD and did a fresh OS install?

Don't O/C your CPU isn't meant for o/c, you'll burn out your cpu causing it to process much slower in the future.

not if you keep it cool. btw the K after the CPU designation annotates an unlocked multiplier, which is in fact designed by intel to be overclocked by the end user.

Depending on the brand of your graphic card, it could be either Entry level or enthusiasts level.
If you only spent around $200-$400 that's the entry level range.
The enthusiast level are from $500-$1500

Flat wrong, look at the list again the gtx 680 is high end and costs $399 and a bit cheaper if you catch a sale.

I have a GTX680, 32gb of ram, and a high end i7 cpu and just like you I have bad performance but only in certain places.
While I think the game could be somewhat better optimized, I think that maybe the overpopulation is exacerbating the performance drops in places like cities since in my experience with the game the big frame rate drops tend to be when I get near areas where people are gathered.

I have the EVGA GTX 680+ 4GB with 16GB G.Skill ram with the i7 3770K @4.3GHz
this all tied to a Asus P8Z77-V Deluxe powered by fatal1ty 1000W PS and have have zero performance issues no matter how much is happening, I've been in 150+ fates and maybe dip to 38+ FPS buttery smooth with no hiccups, freezes or stall, that's on a 1920X1200 24" monitor.

In my experience in the Alpha, Beta, Head start and release, the game has performed flawlessly (when I could log in) it seems to be optimized amazingly well.

Running on MAX FFXIV Settings.

AMD Crosshair V Formula-Z
AMD FX-8350 8 Cores
AMD Radeon 7950
16GB G-Skills
Thermaltake 1000W Tough Power
Thermaltake Level 10 GT Case
Windows 8 Pro 64-bit

The FPS are display within FFXIV.

Max FPS:
135.2
Min FPS:
45.8

Remember, cooling is extremely essential to high FPS.
Make sure your system isn't a laptop and that your desktop has sufficient airflow.

I also speculate that your power supplies may be lacking, and unable to push your hardware when it needed most.

Is checking your PC to make sure it isn't a laptop something you have to do often?
or is it ok if I just check once and maybe put a note on it that says "Not a Laptop" sufficient?

Cooling has zero to do with fps, you can run an nVidia at 90 Celsius all day and get the exact same fps as my gpu on water that maxes at 41 Celsius when overclocked 20%.

A cooler card will degrade slower, and possibly be more stable at higher clocks but not change the FPS even by one regardless of the temps (within normal thermal operation parameters)

Also a check the TDP of the Kepler architecture, it's very low, same as the Ivy Bridge cpu. 750W is more than enough, he could even SLI 2 670's with it and still sufficient have headroom.