Note the power of the pirates - they completely ignore land armies! You could have 5 land army units in a territory, and if you don't have navy, the pirates will attack at +1 and can take away the control marker! Not only that, but you can only take it away from them with a new navy attack! It's brutal.
An attack / defence with a power of 1 is feeble. For this I need to use a whole action?
I've only ever seen this used in desparation or against a runaway winning ally. Better to consider a slave revolt with a strength of 3.