The newer release of the AS fixed the problem. The farming service is back and has got some new features.
1# The farming service is available also for exploded directories.
In the 4.X release of JBoss the farming service was available only for archive deployment. With the new release you can safely deploy exploded deployments too.
In the release 4.X each time a new node joined the cluster, it received a copy of the content of the farm directory even if the application was already deployed on it. This needless operation has been eliminated in the release 5.1.0
3# Deploy and farming service are now synchronized
In the earlier release if you removed a deployment unit from the deploy folder and not from the farm directory, at next startup the application would have been redeployed again. Tbis has been corrected in JBoss AS 5.1.0