As the messages are only print out in TRACE level, you have to verify that the console handler allows at least TRACE messages. In 12c it's configured to only allow WARNING messages.
<log_handler name='console-handler' class='oracle.core.ojdl.logging.ConsoleHandler' level='ALL' formatter='oracle.core.ojdl.weblogic.ConsoleFormatter'/>
This line in the logging.xml allows all message levels for the console like it was in 11g.
Awesome, that totally worked. Thanks!