I like shopping at Prairie Moon, too! I never buy mixes, though because I'm just too particular with my plants. I guess if I had more land and I needed to cover a large area, I would consider it.
You know I don't like the site that you are recommending for two reaons:
1. They do not sell by weight, but rather by what they think covers a certain area.
2. I would not want all those grass seeds in my mixes.
The reason they have more grasses then forbs is to be historically accurate. The tall grass prarire one on the most endangered ecosystems on the planet was historically 1/3 flowers