This alternate oracle dialect is to tell the oracle driver to use updated (clob/blob/etc) instead of the deprecated long. This should allow rundeck to startup and create all tables without issues. Tested on Oracle12c.

Install

copy jar file to:

/var/lib/rundeck/exp/webapp/WEB-INF/lib

cd /var/lib/rundeck/exp/webapp/WEB-INF/lib
wget https://github.com/jquick/rundeck_oracle_dialect/blob/master/rundeck-oracle-dialect.jar?raw=true -O rundeck-oracle-dialect.jar

edit rundeck-config.properties change/add dialect to:

dataSource.dialect = com.rundeck.hibernate.RundeckOracleDialect

start up!

All credit to @ikogan