So much hate in this thread. I personally do this all the time. If you're saying its not viable, you're wrong. As it sits, I have "tanked" as blood dps on heroic morchok, yorsahj, ultraxion, and spine. Sure I may not be pulling the 40k of our shadow priest, but I AM pulling around 30k+ depending on fight, right below our lowest "dps" (resto sham that switches to ele for 2 heal fights). Sure if you're going to try this as a pure DPS role, you're probably not going to be optimal compared to a frost or unholy dk, but if you can learn to do this as a tank, and not get raped in the process you have just become one of the most important people in the raid. The fact that you can pull solid numbers, tank the boss, AND provide a massive 1 minute raidwide healing cooldown means you effectively help as every role in the raid. How many other classes can accomplish this? None.