Guide: Under Molten Core & Uninstanced Zoning
Well, I've made a couple interesting finds in Molten Core, and figured I'd share a guide to open up potential to newer finds off this. You'll probably want to be 80 (for HP reasons), and maybe have a health potion to play it safe. Onwards to the guide...
Above: Step 1: Head into Molten Core, approach the first bridge (but don't go over it) and stand just to the left of it.
Above: Step 2: Now look left and you'll see a steep-looking hill with lava flowing across the surface. This will be your path up. Jump in and start swimming up! Be mindful of your health, jump in and out the lava the entire time you are moving forward to negate damage, and heal or drink a potion if needed.
Above: Step 3: Upwards and to the right you will see a rock... this is platform you want to stop on and heal up or just take into consideration what's around you.
Above: Step 4: This is where we're stopped. Notice anything familiar? It's an exact copy of a piece of the Black Rock Depths instance where you have to run across the bridge to grab your Core Fragment in-order to get attuned to Molten Core.
Well, now you're in an area with quite a bit of potential. Obviously, the rest is up to you, so here's a couple of the things I've found...
I'm not sure where all of this leads, but here's to hoping someone can try this out and chime-in with a good find.