Although characters are still taking an unusual time to load in their portraits, as well as the background & selected character on screen, I'm fully able to login, and change character regardless of them showing or not.
It's not that it doesn't happen on higher graphics, it's that on low graphics it's even worse. Won't even get to load 1 character on startup most times.
It was just a coincidence. Nothing we do on our side will fix it. If not, people wouldn't have the same issue when logging in on a different computer. Or have alt accounts that are fine.