I still see a need for a general "Web Application Frameworks" forum - note, not "other" - in the "Engineering" section for discussions about the pros and cons of using various frameworks and the background information on what these frameworks are and how they work.
If the nuts and bolts questions on how to use Struts justifies it, I could see adding a "Struts" forum - in the "Products" section, not under "Engineering".
Even if a Struts forum is added I'd still avoid having a separate forum for the nuts and bolts of using JSF until the JSF specific traffic justified it. When it did get added, it might go under "Java" rather than "Products", since it logically belongs in the same section as
JSP.