Err, I mean y into the (x,z) matrix of course, lol... It's late...

@Angelouscuitry: Thanks for the detailed tutorial picture! :D
Now I know what your intention is. g
From what you said, I did it right without using IBL ans without artifacts.
Have not used the Poser ball tho. The only setting on the ball except for the math nodes was "forward normals". No groups changed or whatsoever.

More IBL's to have more brightness? that would cost more resources and you still have no good shadows. IBL + shadow casting on 1 light doesn't work very well.
You would make 1 IBL and 1 light that lights the scene and is responsible for shadows. The IBL only gives some tints to the lighitng but it doesn't do the main lighting part. It's set to a low value.