The reason Dk's are doing more AoE damage is because of Pestilence, Blood boil and Death and decay. They have 3 AoE spells, plus with the buff to their diseases Pestilence does even more damage.
Ret paladins used to have Consecrate but it was taken from us. Divine storm takes 3 holy power now, which is fine because we are able to generate it more easily. But the biggest culprit is HotR. We have to have a target targeted and in melee range to use this attack
Make Hammer of the Righteous hit the ground and not a target. Give it a radius comparable to Death and decay or even smaller, doesn't really matter. But us having to run after mobs if the tank moves an inch is just bad design on an aoe spell.
Give us Consecration back as a spell with lower damage. Or even make devine storm cost 2 holy power.
Just my thoughts.