There is no reason for HTML editor to be compatible or incompatible to Adobe ADDT.
The DataAssist update should still work with HTML Editor, as long as you have the same instance name.
Could you please copy and past the DFP Server behavior code and the DataAssist update server behavior code in a text file and attache it so i can see what is causing the issue.
If you could also explain a little bit more about the error you are getting (if any) or the result that you are seeing on the page.