If you post this on the native forum, I'll bet you can get some ideas. Where in zone 7b do you live?

Here is one post.

Here is a link that might be useful: Dry Shade

Phlox divaricata, smooth solomon's seal, tiarellas, celadine poppies, and coral bells all do great in dry shade for me. Some other non-natives for dry shade are hardy cyclamen, epimediums, pulmonaria, toad lilies, and some hostas (though some like the last two would prefer some moisture). I also grow astilbes in fairly dry shade but you have to get them established before they can take any kind of drought.

If your shade is dry because of tree roots one thing I have learned that helps is to water the entire area (not just the plants) and to water deeply to draw the roots down. Frequent shallow waterings just encourage shallow roots and watering just the plants draws the tree roots into the are where your plant is and the tree roots hog all the water. Once I read about this and changed my watering habits I lost much fewer plants. Good luck! -Ais.