Hi,
In jBPM 5.3.0, you need 'org.jbpm.bpmn2.BPMN2ProcessProviderImpl', not 'org.drools.bpmn2.BPMN2ProcessProviderImpl'. I guess the error was caused by old drool-compiler jar in your classpath. So the solution would not be adding drools-bpmn2-5.1.1.jar but making sure you use the latest jars from jbpm-5.3.0.Final-bin.zip.