I'm in the same boat with you... There is a "hidden" world builder that you can access, but it is a pain to use. You have to follow a trick using the Civ V FireTuner to access it and once you do, the tools are limited. You can only draw one hex at a time (time consuming with larger maps) and preplacing civs and city-states is tricky. I'd have to dig for a link to the instructions... they are in these forums somewhere...
Anyway, I am really hoping for an external world builder very soon. I just started my winter break and once school begins again in January, I will have limited time to work on anything. PLEASE Firaxis... release the SDK very soon... It's been a couple of months now...