Are you trying to concatenate the row data into a single bookmark, or will there be 11 bookmarks? I am not sure why GetCellValue wouldn't work if it is the latter since you are working on a single row at a time. In either case, I don't think GetCellValue is going to be an impediment to your speed. You could use ExportData to get a DataTable of the entire worksheet, but ultimately, you're still iterating each row and then editing/saving a new Word doc for each one.

I think the most obvious solution here is;

1. Create an automation to open and iterate through your spreadsheet and extract what you need from it.
2. As you complete a row, add a value into a new column indicating you have processed that column. This can be used when retrieving a row to allow you to stop in the middle if required (or the power goes out, etc...).
3. Create an automation to open (if not already opened), update the bookmarks, then save your Word doc.
4. Create an automation to copy the Word doc file to a new location (this would likely be faster than a Save As in the Word doc and allow you to always operate against the same file in the same location.

Let me know if that makes sense.