Against adsense TOS? (20$ eCPM)

$20 eCPM isn't a problem, I once had a site that was getting like $50-60 ecpm (I won't mention the niche, but what I noticed is that the people who clicked were coming from short-tail search phrases on Google, for example, if someone came typing 'learn how to swim' and the adsense ad title on my page was 'learn how to swim' they would click on it). Scent...what you type is what you click.
 


Adsense optimization team?? How do you get in touch with them...

Dunno how you're all getting higher than 30 eCPM unless you have sites in the Medieval Castle Home Insurance niche

You don't, they get in touch with you. the ecpm's are heavily reliant on the niche but don't necessarily need to be laser targeted.
 
Like blogspotter mentioned, google actually prefers the blending. I have had their "optimization" team send me modified screenshots of my sites with suggested blending techniques. As far as high ecpm's, you should be fine. I have a few sites that have been averaging $100+ ecpm's for years.

If you are worried about throwing up red flags keep an eye on your CTR for each of your channels/sites.

damn, you got $100+ ecpm for years and not getting banned..I just hit $168 eCPM 3 days ago and today google disabled my account, actually my ctr was low only 1-4% and average 700-1800 page impressions/day... still search a guidelines about safety stats for ass-sense
 
I have some old sites that still bring in over $500 eCPM, never had any problems. Low volume though, so maybe they are flying under the radar.