I'm a publisher and having games that I distribute also by GD.
I can confirm that in the last 6 month you need to approach them to get the payment - but at least you get, and their minimum payment is low, not like others who can say minimum $500
About eCPM - it dropped. since the beginning of the year it really dropped. on my website BIBIB.net I used to have 0.13 CPC (EURO) and it dropped like hell. I also see it with the games I distribute on other websites. I can't point on the reason, ADS.TXT or Google taking too much control on the market, maybe drop of value in the entire industry. Don't know. But I've heard about it from some publishers and developers.