Google Apps Domain Level Shared Contacts?
Solution 1:
Google does not provide a GUI to add domain shared contacts. They can be added through the API as you've discovered.
There is a great free tool at is available from SherpaTools that will allow you to create domain shared contacts when you enable their Application in your domain. I think they let you create multiple directories. I have used it in one of our test domains a few weeks back. We build a python app to import contacts into our 60 domains, not recommended. :p
Solution 2:
We accomplish this where I'm at via the Groups option in the Google Apps control panel. Yes, this is build off the old Google Groups system, but you can set groups up to work very much just like distribution lists. The downside is needing to involve your Google domain manager every time you need to create a new list, but once created you can give ownership of the list to someone more appropriate.