I feel that the gold class armor endorsement does not improve your armor that much. I think that if you choose GobiNumb, Assault and Support should have have waaaay more defence.
Using silver defence on my support a front grapple from a non sword using assassin will leave me with about quater health instead of killing, would that mean that it's giving me about 25% better hp? imo that seems rather good for silver.
A Tank with gold, after getting backstabbed, is left with about 30%-35%, as opposed to about 5%. I think it's plenty good.
All that really matters is surviving a grapple/backstab, 9/10 if I'm still alive no matter what class the grappler is too surprised that I'm still alive to defend himself.
I have an assault custom class with the gold level armor endorsement, it's to the point where I can't play assault without it because I'm too used to being able to take so many hits.