Only the TestClass itself is managed by Arquillian and is the only one that will be injected.
You would need to have the TestClass extend the Helper classes or similar for them to be targets for injection.
I had the same problem an created my own Testenricher.
In my testcase the helper-class-member is annotated by my own annotation, lets say @Enrich.
The Testenricher is nearlly similar to the EJBTestEnricher and looks for test-case-members with the @Enrich-annotation.
If such a member is found, the enricher creates and injects the member (default constructor needed!) and then injects all members annotated with @EJB into the helper-class