I've been having this issue as well and I have a very decent connection and never had issues with this game before this. The past 2-3 days when I start getting into dungeons, it starts lagging really bad and I've done literally everything to try to improve it. I notice when I ping it, I get some "request timed out." 25% packet loss and that's from multiple testing.

I hope they fix this soon cause I'm missing out on gameplay here.