Looks like you have some problems with the pasted BPMN2, specifically:
<dataOutputAssociation>
<sourceRef>_2_Output</sourceRef>
<targetRef>First_Event_Response</targetRef>
</dataOutputAssociation>
the targetRef First_Event_Response does not exist, did you miss to set a process variable?
I cannot reproduce problems with signal events on jBPM Designer 2.0 or the latest from master at people.redhat.com/tsurdilo/designer/master. You can with that successfully import for example:
https://github.com/droolsjbpm/jbpm/blob/master/jbpm-bpmn2/src/test/resources/BPMN2-EventBasedSplit.bpmn2
which contains signal events.