I just put a D606 on the rear, and it was the easiest tire I've ever done. A 1 or 2 on your scale. (1 being the easiest). Didn't even need lube / soap. But some of the talc powder from the tube ended up on the rim and I'm sure that helped a little. Had a bad valve stem core so I had to redo the tube, and that took about ten minutes. No kidding.
I've put on Conti TKC 80's and they are not too bad, about a 5 on your scale.
But the tire from hell to remove was the Gripster.. what a pain in the butt. A total cussing and swearing 10.
The fronts always seem to be easier because there's more tire bead. I've mounted Sahara's, TKC80's, and a Metzeler Karoo on the KLR front and they all rate about the same in the degree of difficulty...
Incidently, I got over 9,000 miles out of my last rear TKC80! I was down to 1/4" of tread left, but that's still pretty good for a 50/50 dually tire.