Cody,
You're not alone in your situation. Most anyone who has an in-house SEO role will most likely face the same challenges. There are probably a lot of great articles out there, and others will probably weigh in here. I'll offer a couple things for you to check out to at least help.
What I offer is as much about your need to understand their point of view, so you can provide intelligent, reasonable and high quality reasoning that speaks to their perspective.
http://www.searchenginejournal.com/wake-up-suzy-wake-up-managing-seo-client-expectations/19730/
http://www.searchenginejournal.com/seo-is-a-team-sport-part-1/20206/
And I'll leave you with this:
While SEO should not be the ONLY factor in design, development or content writing, without it, a business could potentially be missing out on vast new business opportunities. When SEO is not integrated into the site process from the beginning, it's just as likely to mean that work needs to be undone or redone if it's going to meet search engine requirements.
As much as developers, designers or content writers may THINK they know about SEO, only a true SEO expert can offer the critical insights and recommendations necessary to make all the difference. And when we're talking about the difference between being on the 1st page of Google results or ending up two or three pages down, we're talking about things usually only the SEO professional would even be able to remember or know about. Especially since search engines change their methods on a regular basis.
Bottom line - asking an SEO expert to step in after something has been done means lost opportunities, increased design'/development/marketing expense, and more.
