I've been a content writer making a living from this business for several years now and once thing I've noticed is in the rush to get great page rankings, people tend to miss the point when it comes to what makes a good blog.
Content Writers Need To Write Well
Sure you need to be aware of the needs for good links and keywords in all your posts, but there's more to it than that.
You need to be able to write well. Think about more than the seo and page ranking. Good content writers are good writers. They give the reader something to think about when they arrive at the client's website.
And that doesn't mean that you need to be fancy or literary either. Get to the point and tell the reader what the client wants then to know about the goods or service that they've got. A good content writer is one that works to sell the goods or service for their client and stays out of the way otherwise.