Low water medicinal indigenous plants is a whole other ballgame and I'd have to do some research there. Ireally want to do a course on indigenous bush foods around here. They are starting to get more into mainstream cooking like wattleseeds. However, we didn't plant our garden with that in mind, only that the natives are architecturally appealing and in keeping with the natural environment as well as food and shelter for birds.
Years ago I used to have a huge medicinal garden with many of the plants you describe - st johns wort, echinacea, borage, etc etc. What we'd call a cottage garden. But that was more in a suburban garden which was more sheltered so easier to maintain and water.
We DO grow some herbs, but let it slide in terms of variety as we just couldn't maintain the garden and vegies and the herbs - seasonally, they take a lot of work pruning and watering and etc. It's not the kind of landscape in which they would grow wild, which is a bit hard to explain. But there's little nooks now where I can get the soil a bit less hydrophobic and plan a medicinal garden, so I'm gonna get on it!!!