Are you referring to a Silverlight RadRichTextBox, as demonstrated on this page
? If so, this is a known issue. Each word is contained within a TextBlock as you mentioned.
Unfortunately we do not currently have a RadRichTextBox translator in Test Studio. In the meantime, the per elements approach is the only method we can offer. How important is it to you that you automate your RadRichTextBox? It is a very complex control. Without a translator it will require quite a bit of custom code to work with it at the level you are asking. It may not be worth the time invested and manually testing that portion of your application may be more productive in the long run.
This has previously been submitted as a feature request. You can track the PITS Issue here: Public URL
the Telerik team