The load balancing of HAJNDI is hardwired:

public class MyHANamingService extends org.jboss.ha.jndi.HANamingService
{
protected Naming getNamingProxy() throws Exception
{
rmiserver = new HARMIServerImpl(partition, "HAJNDI", Naming.class,
theServer, rmiPort, clientSocketFactory, serverSocketFactory, bindAddress);
Naming proxy = (Naming) rmiserver.createHAStub(new RoundRobin());
return proxy;
}
}

This should be configurable on the MBean, e.g.

<mbean code="org.jboss.ha.jndi.HANamingService" name="jboss:service=HAJNDI">
<attribute name="LoadBalancingPolicy">org.jboss.ha.framework.interfaces.RandomRobin</attribute>
etc...