I thought about and believe I tried that w/ no luck. Specifically, I edited my standalone.xml file, added the following and then restarted JBoss before trying the CLI command again.
<drivers>
...
<driver name="oracle" module="oracle.jdbc">
<driver-class>oracle.jdbc.OracleDriver</driver-class>
<xa-datasource-class>oracle.jdbc.xa.client.OracleXADataSource</xa-datasource-class>
</driver>
</drivers>
The CLI command for xa-data-source still did not work. I tried providing "oracle", "oracle.jdbc", and "oracle.jdbc.OracleDriver" as names. I was expecting "oracle" to work.