In addition to above, since all content is so closely tied to how/where it shows up and who needs to see it, versus 10 yrs ago when product marketing would created a set of standard content and post on the website. I would recommend sitting down with Demand Gen team, PR/AR to figure out what is needed for a successful campaign and nurture stream. Then consider one or 2 core pieces of content - whitepaper, webinar or customer video -- which then can be further marketed across the campaign with derivative pieces. Kind of like the core piece becomes the "neuron" and each of the streams that emerge from it in social media banners, webinar based on the topic, a partner video on the topic - all reinforce the thought leadership/essence of the story. It helps to reinforce the message continuously and makes integrated marketing really come to life. 

Product marketing are the experts on buyers and how they buy. Product marketing defines the go-to-market strategy. Marketing (Marcom) develops a plan to support the GTM strategy.

The short answer is product marketing defines the go-to-market strategy to achieve a return on investment. The Marcom team executes the tactics in support of the GTM strategy.