The damage type buffs were always a bad idea. They are very strong and make up a significant bonus to the skill line and power level.
It both Encourages sub classing and makes sub classing less diverse.
The buff basically request each class only deal one damage type. That's boring for pure classing. Bring back poison. Let Engulfing do damage based on the type of staff you have.
Remove the fire, AoE, Shock, Physical, Frost, DoT, and Direct from skill lines and passives. Let people choose damage sets that buff damage types if they want to restrict their playstyle like that.
Ardent Flame and Storm Calling makes no sense to add together, but Draconic Power, Storm calling gives a 7% and 5% bonus to Whirling Blades Execute.
This is what I mean by it both encourages sub classing and makes subclassing less creative and fun.
The team has already done an amazing job at making the DK lines VERY synergistic. Stop making it all bland fire damage. That's not how dragons work and it's bad for pure classing and subclassing.