The point of an MVC framework such as Struts is that all requests in an application should be made through a central control. In the case of Struts, an instance of ActionServlet serves as the control, therefore all requests should be made through the ActionServlet. By going to specific JSPs individually as you have suggested, you are defeating the purpose of MVC and instead are introducing a page-centric design.
So in general, you should never have a user access any part of your application by going to a specific JSP. One exception to this is index.jsp, which should itself forward to some Action in your Struts application (possibly through the use of <logic:forward>. Even if a particular view that you wish to present is static content that requires no setup in an Action class, you should at least use a ForwardAction as opposed to linking directly to the static content.