As it turns out, you *don't* need to burn kobans to get into the League. Rules on the test server are different:
1. anyone gets added to League, you don't have to be level 20 -- I was added at ~16
2. League resets every 24 hours, not every 2 weeks
Your drops may have just been luck, not a different server rate. I'm at level 18 and mostly done with ninja village and no girl drops yet -- none from Dark Lord, and none from the Ninja spy. That included several energy refills on each. Seems pretty normal so far.