Found this pretty close to my spawn:
Yes, that's a naturally formed merged node. The stupid pie chart is covering the other obsidian structure (what are these called, I'm not sure). I have not done anything but looted the chests here, loot was good. The wisp you can see in the background came from this node and it's actually an Aqua wisp which is interesting as like I said I have not done anything here to cause Aqua flux. A total of 3 of those have spawned but after that it spawned 3 Mutatio wisps. The flux was high all the time and didn't go down at all either. I'm planning on making this a combined wisp and zombie pigman farm.