It seems there’s something more than the broken URL going on. It appears there some server side issues in play.
https://us.diablo3.blizzard.com/en-us/profile/MerLock-1557/ is the correct US URL for MerLock.
If I repeatedly refresh MerLock’s armory page, it randomly lands on either the actual page:
…an unavailable page:
…or a 500 page:
Sometimes those three results load quickly, other times they load slowly. So there’s something going on server side in addition to the broken URLs.