I'm full shield and I approve this message. The exception being boss fits. Since boss fights are drawn out, almost no matter what, I have had more success with mako than with gault and torian. For fast leveling off mobs and quickly finishing quests I like to stick with gault (also because he likes it when I'm a money grubbing ******e)
Edit: I also wanted to say that as a tank I found very little success using my tanking companions, however this could definitely be because they were slightly under geared.