Audience retention and session quality is the key to receive a good traffic from Google.
The number and quality of BL is almost nothing if users don’t like your website and close it in a seconds.

CPMs on the stat picture above is shocking low.
What’s geo and traffic source?

About Exoclick CPM:
Yes, it’s a typical situation, when you starting ad campaign, all advertisers accept your traffic, but after short test period, some of them stop buy your traffic.
So, the prices dropping. Sometimes, if your traffic is very good, the prices can up on CPA offers. Typically 1-2 weeks, and you will understand situation completely.