I am not sure if I understood the problem.
Are you using TinyMCE with the forms class?
The class comes with a plug-in for visual editor similar to TinyMCE. There is also a plug-in for integrating with FCKEditor.
phpclasses.org/package/3524-PHP-Plu
...
These plug-ins integrate well with the class, so they do not have the problem you mention.
Other than that, the focus is only given to invalid inputs. If you disable the validation of the textarea inputs you are using in the form, they will not be validated on the browser side and so they do not get the focus. If you set the ValidateOnlyOnServerSide parameter it will still validate on the server side.