There are many types of content some which you should be able to do yourself and some you just need professionals for :
Your Intro Content : First off this really need to be done be an inhouse person that really understands your business and an external keyword researcher may come in handy here as they will be able to assist in site content which uses targeted keywords which in turn will give you a better search visibility and increased traffic.
Blog or Linkbait : Blog content or ‘linkbait’ these pages can provocative or informative as well as been heavy in keywords, The benefits are massive in the e-commerce sector the ability to have product reviews and open discussion without muddying your main site, the opportunity to give away sample and competitions without distracting the buying customer.
International Copy: a common mistake here is outsource all the content whilst not been able to read the content I have seen companies move into other countries only too find out that they have no one on staff to support the emails in that language, the tip here is interpretation not translation.
Industry News : This is a true outsource service, with a News Service you need to keep completely up to date and have the ability to write compelling articles. You can gain authority, repeat visitors and the fresh copy will keep search engines coming back for more and more. a neat trick here is to have a staging server and add you comments into the news before publishing it.