Is Virgin Media generally bad?
I fixed that for you and yes. They are known for having limits on their unlimited plans, using traffic shaping and a poor contention ratio.
I am a fuel rat. Believe me, we know all about instancing and network issues. Last I checked, I still can't rescue any client who happens to be in australia. Found that lovely fact on my drill. Just ask some fuel rats about these issues.
Have you tried recently? One of the recent patches improved instancing issues a lot and a player I know from New Zealand can now instance with Europeans and North Americans when he often couldn't before. I'm in the UK and was in a wing with him and a North American without any issues a few weeks ago.