If you're a vanguard stacking defense, then you're doing it wrong.
I have played my vanguard since day one of early release and have had many build high endurance, high shield and high defense. The parse data does not lie in high defense i take much less damage than any other build i have tried. When i join as a pug the healers of that group always comment on how smooth and easy my tank was to heal and keep alive. Try it out yourself and you will see.