So, lately I've been playing WvW with a friend, and when it comes to a zerg, my computer just stops try to render the game and the FPS drops even reach to 0. I know it's a common problem, but hear me out.
The same friend of mine has a nVidia GTX 1650, an old GPU. I run on a AMD RX 6650 XT. When it comes to WvW, he sais he doesn't suffer from freezes or FPS drop. He also runs on a i5 (don't know the model).
I've been thinking on upgrading my setup, specially the CPU (I have a Ryzen 5 3600), and, as far as I know, GW2 tends to need better single-core performance (even with the engine upgrade). I've been also thinking on selling this GPU and buy a better AMD GPU.
Worth mentioning: I have 16GB of RAM and a SSD, where the game (among other stuff) is installed.
And this is not only on WvW. Sometimes, on Lion's Arch, the FPS drop happens too.
GW2 is extremely CPU heavy, so you want to get the best CPU you can, as you said especially taking into consideration single core performance. GPU is of less concern so you should be fine with what you have I think. I run it on Ryzen 5 1600, and RX580 8GB. It runs alright, but you can really hear it. Biggest effect to me were CPU and SSD upgrades
I bought Ryzen 7800x3d, improvement was huge from Intel 9th gen. Those x3d CPUs are really good at games. But you still have to: disable shadows, character limit medium or lower to keep fps reasonable. You can look for videos using processor you want to buy in GW2 on YouTube.
If you also have solid AMD GPU, you can combine their fluid motion frames with good CPU to get best possible performance in GW2 right now. Fluid motion frames is a frame generation technology that you can turn on in any dx11 game