It is our primary focus and will remain that way until it's fully fixed. Believe me, we feel your pain - it sucks not being able to connect. This is absolutely our top priority until we can verify that everybody who wants to get in the game can. We have TechOps personnel onsite at our new server hardware center coordinating throughout the weekend with our Dev and Platform teams back at the RPG studio, and will continue doing everything we can to fix this ASAP.
We did just make some server configuration changes to Cobalt and Miller to try and improve login connectivity while we continue to work on identifying the root cause - those changes went into effect almost an hour ago (around 2 PM PDT / 9PM GMT on Sat March 14) so if you were having trouble logging in before and A) now can, B) still can't, C) the problem seems alleviated but not entirely resolved, sharing that information here, on the forums or tweeting at Andy or the official account helps us.