I don’t have a specific fix that will guaranteed work for you but you can try a few things.
Does this happen with all characters? Some skills are much less performant than others. For example, Avalanche is a very bad offender that could actually cause an issue like this. We know why it’s happening and have a fix coming down the pipe that will resolve skill based issues like this. I would start by changing your skills and see if that helps. (unlikely but it’s worth a shot)
You can try resetting graphics to defaults by deleting or moving your le_graphicsmanager.ini file this is also a stretch but I’ve seen it fix issues like this before so I’d say it’s worth a shot.
I know it takes longer but doing a file check through steam or a full on game reinstall might be worth a shot too.
After that I would open up task manager while playing and keep an eye on your memory usage and see if specific actions cause it to spike.
I’m sorry I don’t have a more clear cut method to solve this right now. So many computers behave so slightly different from each other. We are working to make Epoch work well on as many as we can but it’s still a work in progress. We’ve seen very quirky incompatibilities, sometimes as innocuous as a VPN. This isn’t to suggest you should turn it off if you have one but just that we’ve seen weird things happen that I wouldn’t thing should affect it.