The Cataclysm expansion is bringing about some changes that will affect certain classes on a very basic level. Hunters, for instance, will no longer use mana as casters do; they will use focus, a mechanic similar to energy. Paladins are getting Holy Power (I will agree with Blessing of Kings and World of Matticus guest poster Rykga concerning the name, “Zeal” sounds much better and allows us not to use the abbreviation HP); I’m not sure how it’s fitting into the UI, but they’re similar to combo points on the caster. Druids will have a built-in Eclipse bar; as they cast Nature spells, they will move closer to a Lunar Eclipse, which will grant them bonus arcane damage, and vice-versa. The runes used by Death Knights will regenerate differently, and the class will only have one dedicated tanking tree (Blood). Warlocks’ soul shards will work similarly to DK runes, but will regenerate verrrrrry slowly on their own, and can be used to amplify certain abilities. Some of the other classes’ trees are being more refined in order to separate them from each other: the Fury tree for warriors is going to place a heavy emphasis on Enrage mechanics to differentiate it further from the Arms tree.
However, some classes are not receiving any of this extensive treatment. Mages, Shaman, and Priests especially do not really seem to have much in the way of new stuff to look forward to. There are some fun-looking talents for sure and they will all be enjoying the new masteries system, but will yet just be using mana to keep casting many of the same spells as before. Rogues, too, while their combo points, energy, and stealth are already quite unique (aside from cat-spec feral druids), will not be getting a lot of the same new-and-shininess bestowed unto other classes.
I don’t blame Blizzard for this in the least, and the changes are of course not yet final; we may see something new for all of those “left-behind” classes. I just hope that they are all just as fun to play as any other, in the end.