Video Card related lag?

I am running Windows 7 with a nvidia GTX 670 using the latest drivers, and ever since the first maintenance after 2.2, during "primetime", namely just after reset and in the evening when people are raiding, I get simply unplayable lag in game.

Running around in a town is choppy, and as soon as combat starts, my fps drop to 1, literally 1... Outside of combat, standing still, 60+ fps. No issues with any other game though...

The interesting thing is that when I get this 1 fps slideshow lag, my GPU core load drops to 0... As in my video card is not receiving any data from FFXIV.exe. Then it will jump up to 20-30% for a moment, it renders 1-2-3 frames, and drops to zero again.

I have reinstalled my video card drivers.
I have reinstalled FFXIV.
I am running everything as admin.
I have even set the CPU priority of FFXIV to Above Normal, High, and even Realtime... nothing helps.

The Tech Support forum was recently wiped clean, so I highly doubt it is worth posting there.
Maybe someone here has encountered this same issue and found a way to fix it? Or is running a similar setup and has found a way to fix it?
I am reaching the end of my rope here. I like this game and the people I play with... but atm I simply cannot play during normal hours due to these technical issues.

How is your CPU running when you see the video drop to 1 FPS? Are your temperatures on both OK right before the numbers drop? If CPU and GPU are both dropping and you don't see alarming temps then the most likely cause is a bad Power Supply. In the old days a GPU would try to ramp back up after the load was gone but now they stay clocked down until you restart your system to avoid further damage to your card.

Had this issue before on a another NVIDIA card. And it was caused by a faulty Power Supply. I know some computer stores can test it for you, and they are usually cheap to replace depending how many watts you need. 700+ watts will be good enough in most cases.

Okay this is pretty out there but. . . for some inexplicable reason, if I have a youtube window open (and even not playing a video) occasionally my framerate will just tank hard. I drop 100 frames, down to 20. It goes back up when I'm standing still and not looking around, but it only goes back up to around 40. It does this until I close my browser window that had youtube open. It only does it with youtube, as no other time has this happened with any other site open. It doesn't even make sense to me, at all. All I could gather for my issue is closing youtube works. I'm 99% sure it's not the same issue, but the symptoms sounded similar.

Like previously said. Check the power supply and also the CPU temps. My laptop did the exact same thing when it was unplugged until I restarted it. The GPU just would not clock back up. Though a BIOS update remedied that problem. It could be something on your board not ramping your GPU back up, but that would still indicate a power supply issue.

I dont think it is a power supply issue.
I just played a bit of The Witcher 2 on max settings. My card ran at about 70C, peaked at 75C, vs its idle temp of about 34C. GPU Core Load stayed above 40% throughout, got as high as 80%.

So if the issue was a faulty power supply, this kind of continual load on the card should have caused whatever this issue is to kick in. But... nothing. Everything ran perfectly.

I'm not entirely sure then. Your CPU temps check out okay too right?

The part I'm finding hard to understand is that you said it only occurs during "prime time."

So your FPS is normal on the off hours? That would seem completely irrelevant to something like frame rates.

The only other idea I've got is to try older drivers instead of the most up to date drivers. Or turning down some graphics settings. Not saying your computer can't run it. But if there's some funny business going on, your card might not be playing nice with some of the settings. Which would indicate an issue on the game's end.

I reinstalled windows not long time ago , then updated system to all fresh drivers ->including<- my video card (i using AMD) . After log i noticed that shadows ingame was showing improperly (like some Squares or something like that) also fps when battle against 3 or more mobs was fall to 10~15 , same if someone else fighted with pack of mobs or just "fating" lol . I was wondered whats wrong , tried many things . In the end reinstall Videocard drivers to older ones solved all problems . At least it fine by me since i play only FFXIV and XI sometimes only ;)

Yeah, I reinstalled the older "stable" drivers, and did bios repair...
Well I can play fine at 6:00pm... the question is 9pm. We'll see.