Deploying multiple Struts 2 wars in a single ear may not work, due to each Struts 2 instance seeing configuration from the other war. Struts 2 doesn't allow multiple configuration files for the same package, or more specifically in this case, multiple struts-default.xml files. If possible, configure your application server to better isolate wars using a child first strategy for classloading.
Wander Grevink reported the following (on GlassFish 2.1):
EAR WAR-1 META-INF MANIFEST.MF lib struts*.jar struts*.xml META-INF application.xml WAR-2 META-INF MANIFEST.MF
Where both MANIFEST.MF files contain the following entry:
And application.xml contains this entry:
All struts related files go into the shared lib directory.