A Battle.net Status report has word that while the Asia2, Asia3, Europe, and USEast realms are back online, Asia1 and USWest remain offline while they investigate what has been causing some characters to revert to level 1 (story). Here's the word:

Asia1 and USWest realms are still down while we investigate what is causing characters to revert to level 1 status, losing all items, experience, skills, and stat points. (Note that this is unrelated to the issue where Barbarians that were always Level 1 fail to load correctly).

We will update again tomorrow when we have more information regarding Asia1 and USWest.

-The Battle.net Team