We had a different experience that might be of use, or maybe not.
Scourge was killed by members of our group in retaliation for his rape of one of the PC's before the Man's Promise was ever taken, so he wasn't part of the final battle. Instead it was Plugg and nine level 2 warriors as well as Patch Patchsalt who took Scourge's place when he disappeared overboard. There were six Rahadoumi sailors onboard as well, but they took a neutral stance in the battle, unwilling to take sides.
The party was made up of four characters, all 3rd level, along with Rosey Cuswell and Sandara Quinn. The group chose to mutiny before they ran afoul of Bonewrack Isle, suspecting that Plugg had nefarious intentions towards them and they needed to act first. Rosey and Sandara were being kept with the officers while the PC's were sleeping belowdecks with the Rahadoumi. The group had also befriended Hartshorn who was kept chained to the foremast.
The Rogue and the Bard snuck on deck and took out one sailor and Patch without the alarm being raised (Charm Person by the Bard on Patch and then his being bull-rushed overboard by the Barbarian), and then they and the Master Summoner went to the officer's quarters - the first two threw open the door as the Summoner began spamming MSII's, filling the cabin with more than a dozen dire rats. Rosie and Sandara made it out and were armed by the PC's - Rosey and the Rogue held the door with the aid of the Master Summoner and the flanking Dire Rats while Sandara joined the Barbarian who was calling out Plugg from the captain's quarters in a long-awaited showdown.
Sandara and the Barbarian battled Plugg while the Bard tried to stay between the two groups, buffing with Inspire Courage. The fight with Plugg was a tough one until he got within reach of Hartshorn and the big man attacked him. He was ineffective and Plugg killed him for it, but the distraction was enough to allow the PC's to gain the upper hand and finish him. Only three of Plugg's men survived long enough to surrender.
The group had the aid of two NPC's (and a third when it mattered) and were a level higher than they were originally intended to be against 9 moderate opponents and 2 whom were very tough. However, they also had no magical equipment to speak of. They had a bit of luck otherwise things could have gone south quickly, but they also planned very well. Still by the end two were near death even after they had exhausted all of their healing.
The storm hit them the following night, and shorthanded as they were they were run aground on the rocks of Bonewrack Isle with Sandara and one of the men formerly under Plugg taken.