Thanks for reporting! I've created a task to investigate this more: https://jira.jboss.org/jira/browse/RF-8246 . As for now you can try setting Maven scope for SLF4J API to "provided" and try.
setting the scope to "provided" works fine. For me my problem is solved but I leave this topic in state "question not answered", okay? For the case that there will follow a "best practice" solution.
You are right, this issue should be resolved because the same configuration with "provided" dependency will fail on another container that doesn't use SLF4J framework.