Really good post man thank you for sharing. It's possible that new advertisers did come in but I don't always take their word for it. Did you also try and re-create the campaigns to see if that would garner you a better position in the ad server?
$0.12 is too expensive for most all mobile offers (hell that's tough for a lot of web offers). Traffic this expensive can work with some of the higher paying sweepstakes offers but you need a REALLY good landing page that pre-qualifies the traffic and then sends them down to the offer were your chance of converting is much higher (ie: sweepstakes).
You're exactly right though that is the purpose of the one-click conversion offers. To get in, learn how to buy traffic, get cheap clicks and becoming profitable. It's a simple as matching traffic with a link - easy. As more competition comes in though that's when it does become time to make your own custom lander on the source to give you more of a competitive advantage (also increasing that barrier of entry).
Thanks again for this post and keeping us updated with your results!