Are you still promoting your blogs in the same old fashioned ways like blog directory submissions and RSS feed submissions? They have become obsolete!
Social media marketing is the only way method by which you can expect search engine rankings. Promoting individual blog posts in Twitter and Facebook are not even enough.
Your tweets should get retweeted;
Your Facebook wall postings should be 'liked'.
You should be a strong presence in Pinterest.
Google plus streams cannot be ignored.
Linkedin profile and participation in Linkedin groups would emit good social media signals.
Blog commenting still plays a major role in search engine rankings.
Go with the present internet marketing trend to stay afloat.