<p>IBM Rational Application Developer is very slow and has many problems.</p>

<p>I tried to use ant scripts to build EAR/WAR files for Websphere Application Server
but it did not work.</p>

My understanding is that you build the EAR/WAR, then open your browser, login to the admin console, then deploy your application.
If my understanding is correct, just add an instance of the WAS server to your workspace, and then right click on the server, select Add/Remove Projects and add your project. This way, you don't have to build the EAR/WAR file at all... Building your project is enough. If the build is successful, then RAD automatically builds the EAR/WAR and publishes the file to the server.
Atleast that's the way we do it.