The way we do it is that the tank that is not tanking Kelseth runs in and body pulls while taunting Valanar. The other tank then taunts Kelseth to him.
So in your case the DK could death grip Kelseth to him. Also at this point you should be able to take at least 1 or 2 hits without needing a heal so maybe your healer can hold off for a second to let you gain aggro. Also you could get druid HoT's (I believe) and/or Disc Priest shield if your group allows for it.
Finally (or maybe first) a hunter should be MD'ing Taldaram to you which should stop any healing aggro long enough for you to build up threat - a hunter should be doing this every fight anyway.
Depends on your group composition in the main. Could you please describe your typical setup? The previous week you may have had a hunter or rogue in your group?