I havent fought any of the worldbosses yet, but they are not instanced - hench you can bring everyone, his dog, his speeder and his wookie, and the dogs companion and the wookies companion, a vendor, the vendors vendor and their companions!
If its needed tho, is another part of the same question...
however I would like to see the groupsize for flashpoints and open world increase.
As it is now, its better to run 2 man + companions, over 4 man.