The comment in the BarrierController proposes a dependency on

<depend>jboss.ha:service=HASingletonDeployer,type=Barrier</depend>

But the tag should read: <depends> ... </depends>

Strange enough, a wrong <depend> tag is ignored during parsing of the jboss-service.xml, leaving user's wonder why the dependency don't take effect. Kudos to Amit for spotting this.