The problem is you went to Dribbble looking for a designer. Dribbble is a website for artists. At first, this idea may be confusing because of their job board and the postings which call for the types of people you may be looking for.

The reason you can't find anyone you want comes down to the very essence of the site: a place for artists to show off their pixel perfect creations on 400px canvases. Artists aren't that great at problem solving, but they can make really beautiful UI and related imagery. Go there when you need pixel magic, but I wouldn't expect to find the kinds of people to solve high level design problems.

You are probably looking for a "design thinker" type. Someone with a brain sculpted by a big consultancy like IDEO, Frog, etc. trained to think about design in terms of logic and creative thinking rather than visuals. But definitely not an artist.

Good luck.