This is what the Blizzard poster Zarhym said about the changes coming to dispels in Cataclysm:
–Druids will be able to dispel defensive magic, curses, and poison.
–Paladins will be able to dispel defensive magic, diseases, and poison.
–Priests will be able to dispel defensive magic, offensive magic, and disease.
–Shaman will be able to dispel defensive magic, offensive magic, and curses.
That’s just dumb. Has lore left the house? It’s a Cataclysm and they’ve stopped caring what we think? Or what they themselves once thought?
Druids are all about nature magic. Obviously.
And Shamans are into the elements, elements are part of nature. So they’re about nature magic too.
Consider that between poisons, curses, and disease, which is the least nature related? Curses. So why are the two proponents of nature magic the ones who can cure curses??? Makes no sense.
Curses are like “dark magic.” “Dark magic” would naturally be cured by “Light.” That’s kind of “Holy magic” then, no?
Paladins and Priests both have Holy specs. Dur. That’s because they’re practitioners of Holy magic. They’re the light that fixes ills caused by “dark magics.” They are the natural classes to be dispelling Curses. But neither does.
Diseases. They’re kind of in the middle. They’re the “dark side” of nature, and cured by the “light.” I’d fine with any of the four curing diseases.
And poisons are naturally of nature and so curable by nature. What’s light got to do with it?
And the magics. Magics are not the realm of nature. Look at the Quel’dorei versus Kaldorei debate for lore here. Magic is man made, not natural. Magic is the realm of men, Paladins and Priests. Nature is the realm of Druids and Shamans.
–Let the Druids and Shamans fix the poisons and diseases.
–Let the Paladins and Priests fix the curses and magics.
But if you got to mix it up a little.
–Let the Druids fix poisons and diseases.
–Let Shamans fix poisons and curses. (Hexing folks ain’t natural, ya know?)
–Let Paladins fix diseases and magics. (Cleansing disease by the power of light’s goodness.)
–Let Priests fix curses and magics. (They’re the most like to be wearing pointy hats.)
Well, that’s what I’d be doing if this were my game. But, it isn’t.
Kinless Chronicles 
I don’t know. To me it makes sense that the two most nature-related healers have special powers to combat the “unnaturalness” of curses. Poisons and disease are an integral part of nature, while curses warp nature. So the defenders of nature have special power to fight curses.
It’s sort of like paladins and undead. Undead are the antithesis of the light, so paladins get special powers against them.
Curses to me always seemed ritualistic and nature… thinking of voodoo magic and that sort of thing… so for ritualistic classes to be able to dispel them… that makes sense to me.
Priests are there to cure the sick… diseases make you sick so that makes sense to me. Paladins are a form of battle hardened priests… and in battle you will encounter poison as a weapon so I get that.
As far as dispelling magic? Well… they are all healers and all of their abilities are in fact magic abilities.
That is my take from a lore perspective…
From a game play perspective… what does it matter? Lore and gameplay took a departure from eachother a long time ago. For the most part this isn’t a bad thing. Following lore creates imbalances that cause more issues. For instance, faction specific classes. Or how about race/faction specific abilities? Devouring plague made Undead shadow priests much more effective than any of the other races… for what reason? How many priests had to reroll dwarfs for fear ward?
Why was it fair that horde pallies dealt more damage as retribution, and alliance pallies were more effective tanks when seal of vengeance and seal of blood were mutually exclusive?
In today’s day and age when most of the devastating boss abilities are magic… how is it fair that only 2/4 healers can effectively save their group?
I agree WoW loses some of its flavor over these types of changes… but it makes up for it in balance and stronger gameplay.
I have to agree with that. Abiding by lore means compromising game play to some degree. And to keep game play interesting, and not stacking the raid full of the new Paladins capable of everything, say, some odd things have to be introduced that just don’t make sense, outside of balancing it for the players.
This is really true, there is a distinct difference between the natural magic and the man/elf/etc magics that should be allocated to appropriate classes.