BitMedia.IO is the best ad network for me. Try using it. Their payouts are pretty high, and their system is very convenient.
As regards the approval, yes it took me about a week to be approved as a publisher, but their support says that it is better to email them and they will speed up the process. I have also heard that they have 900+ requests and they are unable to proceed them really fast.
By the way, they always work on the system and try to make it better for users, I think that Bitmedia has a bright future
I got denied, then I emailed them back asking the reason and they sent me a email with a picture in russian. Then I tryed to contact them back and since then no reply what so ever.