Some tips here are pretty good, a few are really "situation" specific.
Whoever is sailing is more or less forced to a cannon on the stage against the frigates, so thier cannon skills must be decent. Once past this stage leaving the helm could be further dangerous depending on your approach to the bridges.
If you get a few level 30+ pirates with staff on your crew, clearing the dock of officers in the first stage of the battle takes about 20 seconds (all staffs blasting wither) and helps everyone survive easily, and likely not even need to heal anyone.
I won my boss battle with just me sailing, and one guildy at cannons.
I've beaten it with as few as 2 pirates, and as many as 12.
It maybe harder with more people, but you have more firepower.
It simply comes down to who is on the crew, and how well thier shooting, and how well the pirate at the helm is at avoiding enemy fire while positioning the ship for attack of the bridges (and then Goliath).
I have noticed in the numerous boss battle's i've participated that there seem to be 3-4 different approachs from the sailing perspective.
Anyone care to elaborate on thier boss battle 'sailing' tactics? Im a master sailor, but always choose NOT to 'drive' as I havent really gotten comfortable with any method, and i'm usually busy blasting with cannons.