Oozie is cluster agnostic, which is why we require an RM/JT and NN per action in your workflow (or once via the <global> section). In practice, many users use one Oozie server per cluster, so it's an extra burden for them to have to specify this all the time. It would be convenient if we added configuration properties to oozie-site that would let you specify a default RM/JT and NN to use.
This way, these users could completely omit the <job-tracker> and <name-node> fields from their workflows; as an added benefit, they can easily update these values if they ever rename/move their RM/JT or NN. We'd of course still allow specifying <job-tracker> and <name-node> in each action and <global> to allow individual workflows or actions to override the default.