Welcome to the message boards Lawrence.
I did really well with witchdoctor companions except for the fights with Bishop. The Inoshishi Necromancer pig is a really high damage hitter that hits again and again with his mojo echo. He comes with Jobu's Ruse which is fantastic for that second chance when he gets blocked. I give him double Mojo Echo and he commonly hits 4 to 6 times per turn. When I put will boosts on him and a damage boost from my privateer he hits over 2500 all the time. I really hope he will get a promotion as I really would love to give him Mojo Rising since he kills so frequently. His shielding isn't the greatest and Ratbeard's advice of "Protect Your Squishies" is perfect for him. I put a Valor's armor on him and turn him lose and just watch him clear the boards. Many other players have seen him in action and had to get one for their pirates. He is a great one for you. Plus he will be back far enough to steer clear of all those Marleybone foxes with their high degree of burst fire.