NickVanHoeve, I feel for you.
I've been trying to troubleshoot a similar drop in traffic that happened to me around the 17th of August. That long but not-very-insightful thread is here: http://www.highranki...e-2#entry331379
There are so many things that don't make sense about such a significant drop to me, but I find myself so irritated and frustrated that it's hard to put into words.
I did find a fairly good guide by Dan Thies. You may find it helpful: http://seobraintrust.com/perpv1/
I have never done any questionable link building nonsense and my content isn't crap. From what I've read anyway, Google doesn't expect every single thing on a site to be amazing or long or whatever positive "super duper content" adjectives you want to choose. I've seen numbers like 60% of your content should be original.
But at this point in life...after spending over 16 years online and in my time as both a website owner/publisher and a web developer, I have to say that quite honestly, I find most of the SEO stuff just a bunch of crap.
If you ask questions, you'll get best guesses, because really, NO ONE KNOWS. It's all just experimenting to see whether what you do has any effect on the conversions on your site.
Google isn't going to tell you what things they look at when ranking their sites and it all seems kinda silly anyway. Search results are relative to your location and what you have searched for before. While there are some things that seem to be good ideas (like having a keyword phrase in the title of your pages/posts) there aren't a whole lot of things that I can say even the SEO gurus would agree on. And who can argue with them?
Good luck with hiring an SEO "consultant." Where would one even begin to find someone that they think could be trusted? When you do find someone that might be, the fees these people charge is beyond what most webmasters could or want to pay, and it's difficult to even determine whether such a "consultant" really knows anything. (Jill is an exception, I find.)
This forum is helpful, but even so, sometimes the one-sentence answers don't help much to educate or inform. I won't even get into some of the smart a$$ stuff I witnessed here. It's discouraging.
I will let you know that you aren't alone. In the span of the past two weeks, I have finally seen some posts on other forums where people have experienced these major drops in traffic as well. It's not a whole lot of comfort, but I mention it anyway.
I think I've just finally had my fill of much of it at this point. I really think that sometimes it's best to turn off the noise, use some common sense, and put content on your website. Period.