Yeah, as the topic title says, there is a way to get to these rooms from the pandaria continent in 5.4 First, go to this location circled. There will be a bit of terrain missing. Some races with smaller hitboxes can wedge themselves through here. Once you get to the location that I am at, mount on a flying mount with a small hitbox (like a gryphon or windrider), and head south while being under the terrain but not too far deep so that you don't get disconnected. If you watch your minimap, you should be able to see when you approach the boss rooms. Enjoy!
((Note, if you keep getting dismounted at the location shown on my second screenshot, you probably have a flying mount with too big of a hitbox))