Some companies may have marketing teams of far more than 18. Here at HubSpot, for example, we have a team of nearly 100. Even so, we stick to a team structure quite similar to the structure an 18-person marketing team might use -- with one modification. Design is broken off of the Content Team, and relegated to a separate team. This might make sense for your organization, too, if you find that:
It can help, but other degrees also have content writing value. For instance, the ability to synthesize and relate complex information is key to content writing, but can also be acquired from studies in education or philosophy. Companies that offer content writing positions tend to find it easier to train someone in a complex topic than to train someone to write, however. For example, as a healthcare professional with mediocre writing skills, you're less likely to be hired as a healthcare content writer than a strong writer with no healthcare background (but who can be trained in healthcare topics).