Multi-JSF is "not quite finished" in EAP 6.1. I'd rather see you use it though because it is quite solid for WildFly/EAP.next.
I don't have time to go back and test @Postconstruct on MyFaces and EAP 6.1 with Multi-JSF. However, I do have a test app that uses WAR_BUNDLES_JSF_IMPL and @PostConstruct. I know that it works. I'm attaching the maven project for you.
InjectionTest.zip 8.4 KB