Use an ear for every application instance and for their distinct resources. Configure an own loader-repository for every ear with java2parent delegation false.
Deploy the common resources in a separate .jar without defining a loader-repository (or put them in the server/lib ;-)
That should make it.
Thanx Frito, it works now!!
I thought I defined separate loader-repositories for my EAR's, but I missed the java2parent-directive.....
In addition, I had to place my EAR's directly in the deploy directory; can only define separate loader-repositories for top-level classloaders.