I worked out my math up their prior to Lich King release. But checking the math again still, i'm preferring that sword of his over the staff. 160 spirit does not equal 63 crit rating. Im not entirely sure since i cant find any direct math conversions, but ive tested it earlier myself by removing certain items with X crit rating and comparing the Crit% loss with removing an item with Y spirit. Near as i could figure it takes about 3 times as much spirit to match a crit rating. and Thats with our Molten Armour up and glyphed.
Maybe with that fire spec i linked in the other thread since i gain full rank of Student of the Mind. I'll look into later.