I’ve updated my mining guide to 600 for Mists of Pandaria to include a 500-600 route in The Jade Forest. Please remember that regular Ghost Iron deposits will turn grey at 595 and you will need to level off of Rich Ghost Iron deposits. Both are found on the same route.
I have also added an alternative smelting route from 500-525 for Ghost Iron Bars which should be substantially cheaper than the Hardened Adamantite Route.
See the WoW Mining Guide for more details.