I’m actually inclined to agree with you there bingofind, big agencies and middle sized affiliates don’t mix well, there are a lot of agencies that run the pile them high model and just drain little accounts without doing very much at all. Not all agencies just some, I remember walking out of an interview at one that did just that because I essentially saw that as their business model and didn’t want to kill my career that way 
But, having said that, an agency with a gambling department or at least someone who has worked in this sector is essential. I know that a lot of generalist SEO’s that don’t work in competitive markets just don’t get what they need to do in iGaming.