I've recently analyzed an Oozie heap dump obtained from a customer's production job, using jxray (www.jxray.com). In this job, Oozie's heap consumption is ~6GB, and it turns out that nearly 25% of it is wasted due to a large number of duplicate strings. The screenshot below, taken from the jxray report, illustrates the problem.
It turns out that a lot of duplicate strings come from the oozie's own code, i.e. org.apache.oozie.*. In particular, the top data field wasting memory is org.apache.oozie.StringBlob.string (wastes 2.6%, or ~160MB). From the source code of StringBlob I see that it would be trivial to intern (deduplicate) these strings by adding the call to String.intern() in the constructor and a few other places. Similarly, various fields of org.apache.oozie.WorkflowJobBean and WorkflowActionBean collectively waste a lot of memory, and can be fixed in the same way.