I just went to Forgotten Vale Overlook via the paragon portal. There is a view of the inner sanctum balcony, but nothing else I could find. Anything of interest there? I am afraid to go to far towards the ledge for fear the waterfall will sweep me over the side.

All of these paragon places have at least a loot chest.
Some have extra goodies..

Been a while since I did it so apologies if this is wrong. You need to go past the waterfall to get your treasure, it is on the same side as the portal so stick to the right side and try not to fall off, it is just around the corner a bit. Climb up a bit if you can. I actually went down from the sanctum balcony and found it before I used the portal stone, there was nothing there for me, I had already taken it.