My sedum -autumn joy- gets floppy if not watered on a reg. basis and it is well established. Coneflowers do fine without attention on a regular basis for me. I would also recommend black eyed susans/rudbeckia, those seem to take well with little water. Also, you could add some of the lime green hosta, those like the sun just fine and do great without attention!Oh...and yes.....daylillies...I never water mine and they hold their own VERY well (yet,....they are VERY common!)

Just my opinion....I am no expert like many on here but thought I would try to get some responses flowing for you!
bec

Here are a couple of thoughts...Dogwood-especially a variegated variety like 'ivory halo' might need a fair amount of water. The smokebush is probably the tallest shrub you have listed-so I would put that in the very back. Purple emporer is an awesome sedum-but I have mine in light shade and water it a lot-so I'm not sure how it would hold up with little water.

Russian sage, catmint and black-eyed susan would be other good choices in addition to the sedum, coneflower and daylilies. Maybe Joepye weed and karl forester feather reed grass as well?

You might want to look up xeriscaping for other plant ideas for our area...

Here is a link that might be useful: NDSU site - Xeriscape Plant Selections and Ideas