Well, you have the ram for it.
Is your connection being shared with anyone else? Ping is fine but if the packets are being delayed overall by someone else that ping is going to vary. Open up cmd.exe and type in the command line ping -t 46.4.59.55 and check the results that ping back from the Ravenloft server.
If it's consistent then your basic internet connection is fine, in which case..
Are all your video card drivers up to date?
If someone else is gaming on your connection, are you able to investigate which ports their programs use compared to your own?
If you open up your Resource Monitor via the task manager, are there any programs that are using up your bandwidth as you play? Is your Windows Update fully up to date or is that downloading in the background? It should only be the programs that manage your network & whichever programs you are currently using open. I know i've had issues with chrome.exe at work not closing properly when it should be closed (to the point of lots of multiple copies in Task Manager *_*) and I've had to manually kill those chrome copies to regain some semblance of internet stability.
There are a few things that can cause IG lag, so cover all these bases first and that'll make it easier for someone more knowledgeable in this to deduce where the lag is coming from.