That said, I've tried a couple of em, and AdSense still out-earned.
Have you tried using DFP and letting Adsense compete against your Ad Networks? In my experience for small sites DFP (Adsense + Ad Networks) < Adsense However, for sites with lots of traffic DFP (Adsense + Ad Networks) > Adsense
Of course it depends on which Ad Networks you are using. Tribal Fusion does really well for me. Also depends on your niche. If you are getting high CPC from Adsense you don't want to bother with CPM Ad Networks which will only pay at most $1.00 CPM
Because I think that ecosystem - sans AdSense - is all tried, I should think by many if not most webmasters of yore, and concluded not worth the time/effort it requires to maintain it. Unless you have a team of ad-execs working for you.
Agreed. Learning to use DFP is a very difficult task. Monitoring many Ad Networks is a time consuming task. That said, the ROI is worth it for high traffic sites.