It sadly is. On Normal defense is good. On Expert it's very meh despite its buffed effect. On Master its just not worth it at all.Is defense really that pathetic compared to damage?
I recall someone even made a vid about it. Stacking all possible defense stats and seeing how many hits they can survive in Master mode vs hardmode bosses and certain hard hitting enemies.
It's not good .. not good at all. It's way better to invest in Damage/Crit or stack Dodge accessories - despite their randomness they are of more help than defense stats on higher difficulties.