I'm also no expert on Maven but I spent a day trying to figure how to get maven-gfe-plugin to set the classpath properly but didn't get anywhere.  In our meeting yesterday, we decided to go back to the original maven-glassfish-plugin, mvn glassfish:run, that sits outside the embedded project.  
So continue to use
   <plugin>
        <groupId>org.glassfish</groupId>
        <artifactId>maven-glassfish-plugin</artifactId>
     </plugin>
Sorry for the confusion.
Jennifer
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