Honestly, you're going to struggle to get this done in a static Excel file. The first time you email it out, you've got as many copies as you have collaborators. It instantly loses its value and becomes an organizational nightmare.
If you can, think about moving into better platforms for collaboration. We use a combination of Google Docs, Google Spreadsheets, and Basecamp, and have carried out audits many times bigger than the one you're describing.
Here are some basic concepts that will help:
Content review and project overview should be in different channels
You can't fully discuss the content changes in a spreadsheet like this. You'll see that there's a link in the table below to a Google Doc. Every page on the site gets a Google Doc (preferably organized in the same folder structure as the actual site) All the collaboration around content editing takes place in there. Use the 'Notes' section in the spreadsheet for operational communication. (It's worthwhile setting up a template page that all content review docs are made from. It might contain things like; room for metadata, q&a checklists, links to relevant docs, basic instructions for use)
Task management should preferably be in a separate channel
The 'Next Action' column in the table below might work for you. You've got to be on top of it all the time, but you can make a combination of spreadsheet statuses and email work. Using an external task management platform, Basecamp being a good example, makes things a lot easier, and takes the strain off the spreadsheet. You don't have to use Basecamp, but the minimum requirements are that you can create tasks that can be associated with projects, assigned to people, and given due dates. The ability to comment on and discuss a specific to do item (a Basecamp feature) is also really valuable.
Own the Spreadsheet
You can't just send out one list of instructions once. You have to continuously work to make sure people understand and are actually making use of the doc. The version you start out with will rarely be the one you end up with. Review frequently, remove dead wood, tweak, fix, add.
Below is a start point, to give you some ideas. I also use a meaningful color coding on the first, 'Status', column to give the 'at a glance' effect you mentioned. This combined with sorting and filtering, gives you a lot of power.
download bmml source – Wireframes created with Balsamiq Mockups
I should point out that there are several tools out there that will allow your to carry out all, or most, of the actions I've described here. Many online project/task management tools will provide you with the infrastructure to carry out this kind of collaboration. The problem with these tools is that they're often expensive, and require a lot of commitment from teams and work from PMs to integrate.
I recommend first piecing together a solution along the lines I've described. That way you evolve your own methods, and then if you decide you need something more robust, you have a good understanding of your requirements when you go shopping for other platforms.