Massive framedrops while playing

Hello,
I have recently started playing FF14 again after months of inactivity, but I noticed one problem. When I run Palace of the Dead (not sure if the problem is in other instanced duties), I get massive framedrops (from 60 fps to 5 fps) for a few seconds, then it stabilizes back. This happens every few minutes. The weird part is that I have the same machine as before and I don't recall this sort of issue when I played this game. The only change that happened in the few months I didn't play was a complete reinstallation of Windows 10.

Now, my specs are not the best, but I shouldn't have problems running this game (and most of the time, I hit 60 fps on high). I even tried to change all settings to the lowest and these framedrops still happened (even from 120 fps to 5 fps).
I already tried changing antivirus, disabling AMD Cool n' Quiet and tried changing settings on my CPU. The temperatures are fine on CPU and GPU, so it's definitely not an issue with overheating.

Is there anything I can do to make it go away? I tried playing on my notebook and it runs without issues, but it's not as good as playing on a desktop PC with better keyboard and mouse...

Specs:
Motherboard: Asus m5a78l-m/usb3
CPU: AMD FX-8320E eight core processor
GPU: AMD R7 370 2gb OC
RAM: 8gb Kingston DDR3

From personal experience, usually something like this means something is messing with or taxing the graphics subsystem/hardware -- not something inherent to the game its happening in.

Although it almost goes without saying, do make sure your graphics drivers are all up to date, and that any power saving features are turned off. Next step you can try: Run the game in true fullscreen (not borderless window) and see if it still happens. Remove all start up items and ensure nothing that isn't absolutely essential is running, even in the background. etc. If either of those solves the issue, work from there to figure out what's dragging it down.

If it actually is some weird thing in FFXIV causing the slowdowns... incrementally mess with the settings and see if one in particular has a big effect on it.

Good luck.

The issue only happens with FF14 on my PC, so I'm not really sure if it's not tied to the game (hence why I'm posting this here first before going to AMD support).

I already went back to WHQL drivers for my GPU, since I was running newer ones. Nothing changed. Tried running the game at fullscreen (I usually play on borderless windowed), but it's still the same. Apart from antivirus, Razer Synapse and Lightshot, there's nothing running in background.
Tried changing all settings to the lowest of the low and changed resolution to 720p, the framedrop still happens.

Thanks for your response though, I think I'll reinstall Windows and see if it resolves my problem.