Frequent Frame drop after Nightfall update

The frame rate frequently drops to about 60 FPS for a few secondsbefore returning to normal, causing noticeable visual stuttering. This occurs most often when players gather or when I'm being hit by multiple enemies. But sometimes it seems random. 

I never had this problem before the Nightfall update, and I didn't change any settings. I have also heard that other players are experiencing similar issues, please notice this issue asap.