As a Swarm
The Pirates' strength lies in their infamous dirty tactics. They have a low health/armor pool, but possess great speed. To balance this, Pirates can quickly deal a terrifying amount of damage, though they often require a distracted opponent. Pirate Captains require cover or breaks in combat to reload their blunderbuss. Skirmishers need those to light and throw their kegs. Sharpshooters need cover to aim their rifle, and reposition. Providing opportunities for your teammates to flank enemies, reload, and unleash gunpowder hell will lead you and your team to success. The scurvy sea-dogs of the Pirates also need to know when to fight, and when to shamelessly abandon ship.
When carrying the Grog, Pirates should stay on the move to ambush enemies in close quarters. If they're flushed out to open areas, Skirmishers and Sharpshooters alike should try to take down Archers who may pick off their carrier. A slow Viking or Knight trying to chase a Skirmisher with the Grog should be easy pickings for the rest of the Pirate crew.
When fighting over booty, victory is won by blasting enemy defenses with kegs, finishing off the stragglers with firearms, and making off with the booty before they can recover. When defending, kegs also make a great defense by blasting an overwhelming enemy attack. When not blasting enemies, Pirates should send scouts to warn of enemy attacks so their Pirate shipmates can prepare ambushes.
Last Team Standing
In a fight to the Last Team Standing, Pirates should immediately abandon their starting point and set a course for another team to avoid being surrounded. Skirmishers should bombard enemies with kegs to keep them back early on, then flank opponents to distract them from Captains and Sharpshooters who should finish them off quickly, before spreading out to reload, then regroup.
When trying to raid territory, Pirates should maraud between territories to catch would-be reinforcements and charge their specials, then blaze into an enemy territory to plunder it for all it's worth. Rather than mount a defensive, Pirates should keep moving to other territories to stay one step ahead of angry land-owners.