I don't think they will nerf DK's because of this cause they have said many times in the past that the game is balanced around 85 content not lower lvl content. Which means ya a Dk may be able to solo old things but his skills in a 85 raid are the same as a warrior, pally, or druid. The only diffrence is instead of a shield he uses bubbles and heals which give him better soloing tools.