Sudden FPS drops and graphical lag - Acer EI272UR

sleeps1007

I have the Acer ei272ur just upgraded from a 1080p and was loving the 1440p 144 refresh rate. I started playing diablo 3 under the native 1440p setting 144Hz and g-sync enabled and when i encounter large group of monsters I noticed my FPS dropped. It was doing around 110-130 avg but soon as a large group happens it goes down around 70-90. Still can be smooth experience but I never expect it to drop that much. Also, when in a large group my graphical interface seems to lag. If I'm getting 70+ fps there should not be any kind of lag so I tested under 1080p 144Hz and my fps of course increased overall but I was still getting a lag. Basically I'm not worried too much on the fps but I am worried more on the lag. I've tested other games with large groups such as path of exile and doom and no lag so not such why it only happens with diablo.

My Specs

MB: Asus ROG Strix B-550-F

CPU: Ryzen 5600X

Graphics: GTX 1070

RAM: !6GB OC to 3200

OS: Windows 10 Version 20H2

//Edited the content to add model name on title.​​

sleeps1007

Is anyone able to assist with this matter?