It is relatively rare. We've known about it for a bit. The wiki is working on an extensive map project here. The project is not live yet and well, I can't work on the wiki much until next week. Feel free to add photos, maps, and guides to the list in a way that is consistent with other up-to-date entries.
As for the puzzle, you don't need two people to solve it, but it certainly makes it easier :P. You use the rocket puppies' rockets (not there in the photo, they have been killed) to bust the ghost blocks. Certain weapons (like a long fuse bomb as you say) will also solve it solo.