Here is the link to testcase https://docs.google.com/open?id=0B1YALB8JpmN7NVRjWmUyWlgyUzQ
Note that you need to have installed GWT plugin to be able to reproduce the issue. Otherwise incremental publish works OK.
To reproduce the issue do full publish on the configured server throug eclipse and look to the WEB-INF/lib folder. You should see all the jars and project. Then do incremental publish and after it you will see only jar4.jar in the WEB-INF/lib folder.