I did a search: JHB to Buenos Aires in November for 60 days. http://adioso.com/za/johannesburg-za-to-buenos-aires-cr-in-n...

On flysaa.com (Star Alliance member) I can get a cheaper direct flight. Not sure what logic was coded to determine which result receives preference (i.e. ranking) in the results.

I also usually use http://flisea.com/ to search for reward flights on Star Alliance airlines. Not sure what API to linking to - perhaps you could check it out.

Or perhaps, change the purpose of the site: Find the best available reward flights on One World, Star ALliance and SkyTeam over a specific period of time. It's focused and a big need for frequent travellers