I really like the idea of the runes and the interesting masteries. With that in mind, I truly feel as if you should put less effort into a tanky build and more into the armor penetration and more damage. Another suggestion would be sword of occult if you are doing THAT well, especially with the tanky build. Spirit visage is a superb idea, as well as bloodthirster; I would drop the Randuin's for more damage though. More damage would extremely benefit from your armor penetration!