Armour effectiveness

Armour in this game is feeling very Demon's Souls for me i.e not great. I have 30 VIT, +10 Gyrm Armour and Smelter stuff giving me 1000+ Physical Defence. Never have I had such a high defence in a Souls game but I still take massive damage.

I don't know whether there's a crazy algorithm for calculating damage per defence point and above a certain threshold it becomes redundant?

I'm thinking VIG is more important for soaking up damage or maybe a happy medium between that and VIT. I've been watching ENB's playthrough and he seems to favour VIG (his current build has 40 VIG and 6 VIT) and is surviving more blows than I am at a similar SL (with 16 VIG and 30 VIT).