Custom module unable to find JDK class such as org.w3c.Node in EAP 6

Issue

• I'm trying to deploy a .war file to EAP 6 and run into a java.lang.NoClassDefFoundError: org/w3c/dom/Node. As far as I can tell, this class exists in rt.jar that's part of Java 1.6. I've defined a module called my.module that holds JAX-WS classes.

Caused by: java.lang.ClassNotFoundException: org.w3c.dom.Node from [Module "my.module:main" from local module loader @105d88a (roots: E:\jboss-eap-6.0\modules)]
  at org.jboss.modules.ModuleClassLoader.findClass(ModuleClassLoader.java:190)
  at org.jboss.modules.ConcurrentClassLoader.performLoadClassUnchecked(ConcurrentClassLoader.java:468)
  at org.jboss.modules.ConcurrentClassLoader.performLoadClassChecked(ConcurrentClassLoader.java:456)
  at org.jboss.modules.ConcurrentClassLoader.performLoadClassChecked(ConcurrentClassLoader.java:423)
  at org.jboss.modules.ConcurrentClassLoader.performLoadClass(ConcurrentClassLoader.java:398)
  at org.jboss.modules.ConcurrentClassLoader.loadClass(ConcurrentClassLoader.java:120)
  ... 48 more

• Deployment failes with NoClassDefFoundError: javax/crypto/Cipher