I've done probably 30+ frag runs this ladder so far that have been portals, and I've found 1 Black soulstone, and then on top of that I've done at least 12 uber runs, and nothing from them. I like the fact that I have to work for these items instead of doing 1 run and finding it all. Now that being said, I feel as though Uber's and omegas should be just SLIGHTLY higher than they are now, not too much, but enough where you find them just a bit more frequently.
Just my thoughts