All of this... All of it. Makes no sense. Please try making sense next time you post something.You're not taunting the boss. You're taunting the ghouls. This shows that you have zero experience with tanking current endgame.
All of above is meaningless. DS shield is a follow-up to damage, after the damage has already been taken. Unlike blocking with shield it won't help you if you have been killed due to too much incoming damage in a burst. It's merely a tool to not be a mana-sponge tank, which is going to matter a whole lot more in cata. Finally essentially no bosses do consistent powerful spell damage on tank. All bosses but a couple of gimmick ones do consistent physical blockable damage.
At this point, anyone with half a clue will tell you that DK tanks are the weakest both in 5 mans and in raids. The problem isn't limited to them being the biggest mana sponge and most bursty tank, but also to their utter lack of usable-on-demand emergency buttons such as AoE taunt and shockwave and finally their new convoulted resource system which tends to leave them starved and unable to generate threat when pull doesn't go according to plan.