Despite the fact that I was a Marauder, and spent the time constantly attacking the enraged Goobbue, I couldn't get it to attack me in return, for the entire quest it focused it's attacks on the Conjurer.
The only enemies that targetted me were the others who eventually showed up.
It's silly having the Conjurer saying stuff like "leave the healing to me" where as in reality, the Goobbue was pummeling her constantly and completely ignoring me. She was the 'tank' in the situation and I was receiving no damage.
you should probably put some sort of aggro handicap or similar in place here so it doesn't turn out that aggro cannot be taken from the Conjurer despite constant attacking by a Marauder.