Not sure how Blizz managed to allow this to go live, but there's a spot on the Island of Thunder where you can just ride into the Lightning Vein Mine, through which you can access the Stage 3 area including its mobs and some of their related achievements.
A couple of my guildies had been getting said achievements and I was curious, so I went exploring a bit on my Water Strider and I could just ride on in there.
Just posting this here to get some attention to it, hopefully for a fix or something - has anyone else found it? I don't want to post exactly where it is because it's probably against the rules here. It's so blatant though, almost like it's intended.