They often come in groups of 2 or 3 and can break your shielding very easily. The best way to hunt them is to be in teams or go as a single paladin. A paladin of level 35 or higher can take all pirates easily except for Pirate Corsairs who have nasty Throwing Stars. Pirate Cutthroat's pistol shots (single square explosions) are the only thing a paladin has to worry about and it isn't frequently used. They often miss, as well.