First change out everything for impenetrable. Then get rid of the robust rings and get arcane.
As a dk, go for cost reduction. Your sustain comes from dropping ultimates. Your stamina recovery comes from spamming igneous shield.
I would also lose all points in block expertise and change them to hardy & elemental defender. I would also do 1 spell dmg enchant only and have two magicka cost reduction enchants.
With tava, i'd try 5 light, 2 medium and have shuffle/elude on the back bar, you need major evasion for it to become effective.
Purple tristat should bring you up to around 15k stam as a dunmer, which is enough to make helping hands efficient.