Can the OP put up a link to themself because you are quick to blame the pally but I have had trouble with many DK's threat being so low I actually cant release then my white hits were more threat than they could output.
One was a friends alt and when we investigated he rarely used rune strike and his spec was off. Never had a problem since he fixed it.
Remember taunt only puts you on focus and equal with highest threat for a window you still have to actually generate a threat lead which means using all your high threat moves.
** Remember Warcraft players fail in directions you never thought possible.