Okay, this may be a little out there, but bare with me, I've actually been thinking this through for some time, and it seems like this would be a large improvement over the current combat system we have.
1.) Change Exorcism so it does not cause an automatic critical hit against undead and demons, and change Holy Wrath so it works on all NPCs. This was very useful in Naxx, and a reason that Ret dps was so high there, which is why they made the change to Exorcism being an attack that works on all NPCs in the first place. Normalizing it would not cause any major issues, as well as freeing up the added bonus to the attack, allowing for other benefits to be made. The Holy Wrath change is addressed in number 2.
2.) Create a talent in the 6th tier of the Ret tree called "Exorcism of the Unjust" which would read something like "Gives a 25/50% chance that when Exorcism deals a critical hit, your next cast of Holy Wrath will cost no mana." This would let us actually use a useful attack, which would not just be a nuke because of the way mana regen is working for us, and would give us something to look for, an added bonus and proc based attack.
3.) Reduce the damage done by seals slightly, as now we have another attack to use on occasion, and having seal damage as well as another attack to use would probably push us to the side of being OP.
4.) Increase the cooldown by 2 seconds, but change Divine Storm back to holy damage. It is our 51 point talent, and should at least be something more than just another 110% weapon strike. Do something like remove the inconsequential healing that it does in exchange for the switch back to holy damage.
5.) Add another talent into the Ret tree, probably in the 10th tier called "Wrath of the Holy" which would read along the lines of "Gives a 25/50% chance that when Crusader Strike deals a critical hit, the cooldown on Divine Storm will refresh." This would give us another ability that allows us to have a more complex battle styem, while giving us another ability to watch out for, making paladins a little less faceroll and a little more skilled to play.
Applying these changes would give paladins a slightly more complx system of combat, making us more fun to play, as well as staying away from being so frontloaded because of the reduction in seal damage, because as of right now all we have to do is blow cooldowns and let's be honest, seals are a substantial damage dealer for us. The added proc based talents and the addition of Holy Wrath to a regular rotation would also make us much less of the "3 button facerollers" that rogues seem to think we are.