I am not sure how you feel, but I strongly belive that content marketing is more than just writing.
It is:
• Content research
• Interviewing experts
• Figuring the angle to take
• Storytelling
• Outlining
• Rewriting & editing
• Nailing the voice
• SEO optimization
• Content distribution
• Content repurposing
It definitely isn't ;) These are just some of our strategy at Instant Logo Design
By the way, how does guest blogging sounds? Whether that's for link building purposes or for personal bloggers' strategy, I think it can still be a part of content marketing strategy.