How many hours of sun?

I wish I could give you a better answer, but I don't pay much attention to that area. It's on the corner, between the street and sidewalk and shaded by large an oak tree branch. I'd guess it get's several hours of morning sun, dappled light throughout the afternoon and maybe another hour or two of sun in the evening. I should note that it's possible the iris do so well because they get plenty of light in the spring before the tree fully leafs out. Maybe that's the key to their success? I don't have any experience with Russian Sage, so I'm wondering if they like to bake in sun for 8-12 hours. If that's the case, it won't be a good spot for them.

"I don't have any experience with Russian Sage, so I'm wondering if they like to bake in sun for 8-12 hours."

Yes. As much sun for these as you can possibly muster. Otherwise they will be too floppy.