Hello,
I faced a similar problem and was able to sove it by using 'AdvertiseSecurityKey secret' on the VirutalHost config in httpd.conf and
<subsystem xmlns="urn:jboss:domain:modcluster:1.0">
<mod-cluster-config advertise-socket="modcluster" advertise-security-key="secret">
in domain.xml for the ha (in your case full-ha) profile..
Hope it helps.
Also i am using mod-cluster 1.2.0.final with jb71.1. final with httpd 2.2.25