I've found that friends can't join you in any dungeon that concerns a promotion quest. I'm not sure if I remember if this is considered an epic battle ( where you get to chose your companions or not ). I suggest that you set your companion order to 'In Order'. This is found under Options/Game play and choose your strongest companions to assist you. As a Buccaneer I suggest you use Bonnie Anne, Peter Quint, and of course Ratbeard will be joining you. Take the time to use Leviathan's Call, Have Peter use his buff, wait for them to approach so that Bonnie can Overwatch and Quick Draw ( if you gave her this) and then use her Scattershot. I hope this helps you.
1: quick draw seems to be broken, 2: i would suggest quint, barnabus, and (as required) ratbeard, (for barnabus i suggest hold the line two and bladestorm two (since sometimes its hard to find good powers for him/gerard)
What companions do you need for this battle when you're an Privateer?
Salty Tarlac WardLevel 57 Privateer
Privateers have a very good selection for any battle and at your level, you have good buffs to enhance damage or give protections. I would suggest that you use your best melee companions. ( with RB, of course ).