Well I can't say my DPS have as much +dmg as yours do, but I have yet to ever peel aggro off my DK no matter how much damage I front load (even a flame shock + lava burst combo).

My cast sequence for tanking is:

/castsequence reset=target Icy Touch,Plague Strike,Pestilence,Blood Strike,Death Strike (Thinking about changing blood strike to blood boil though)

And yes, I can do an EM+CL on something after dropping a DND and hitting icy touch (which happens almost at the same time) and not peel aggro off. Not sure what your talent spec is or not but I definitely haven't had issues...dunno. Obviously we've experienced things differently. Once pestilence hits (which is only what, 3s after combat starts) then I could do 4x EM+thunderstorms if I wanted to and not pull aggro off - not to mention my DK does more damage then any of my shamans.

I only tanked with a Paladin in BC but didn't find the overall experience much easier. Maybe I just like the tanking "method" of the DK better, not sure