Lately, I've not had much luck either way on chat. It's been inconsistent regardless of login access point for the whole time we've seen problems (not surprising if it's a server issue). If someone's found a fix, I'm all ears.
As for login, I've actually been using the South Carolina access point myself with no real problems beyond what I see on other ones. In fact, it's a bit better than many of the others I tried after the updates.
Now, prior to the recent "fix," I found Taiwan to be the least laggy for me, but could only consistently access HQ on one of the Chinese ones (and not always the same one!).