I fully understand what you are saying and I thought long and hard about this, I was forced to move the title to the blog content area due to SEO advantages. My research suggested that Google seemed to like it better when the posts were in the hatom format – http://microformats.org/wiki/hatom. The entry title had to be within the hentry to make each post conform to this microformat making it easier for search engines to parse and make sense out of post details like title, summary, thumbnail etc.
You can change the tagline for each post by having a custom field named mo_blog-tagline entered as shown below –
If you want the post title to display post title instead of the tagline, there is some discussion here (will lead to creation of two headings with entry title, h1 in content area and h2 in the top title area – again not sure SEO gurus like this) –
Let me know if you have better ideas and I can help.