Paladins, all things being equal (ie at level 60) get demolished because they can't do any damage worth note. On the raids I've been on the paladins hang back and heal their allies for that very reason. At one point in the molten core, the guild I play with (I don't have an account, I use friends) got all but wiped at Lucifron, then they just had the paladins rush it with some priestly help, needless to say the paladins got turned into several piles of nothingness after doing a grand total of 1% of his life.
I admit I was a little bit hard on Rogues but I don't think that they should be the melee damage doers. Warriors should be the paragon of melee. this isn't to say that other classes shouldn't be competant with melee it's just that the fact that rogues and hunters are seperate classes is questionable. Rogues are usually the ones who stand behind the warrior and punt a crossbow into sombodys back. Most rogues that you find in fiction and fantasy are the type to use bows before they use blades because they are, at the most basic level, playing to win, and that will generally cause the rogue to use "cheap shots". there is a difference but there are rogues who when both classes are maxed (Warriors and Rogues) the Rogues can have more health and can do more damage, if they had plate they would be able to be a better tankers than the warriors.
You say I'm asking for Warcraft 4. I am, because with WoW people won't want the world to either vanish or change to the point that their stuff will become useless. And because if they did want to have a story between 3 and 4 they would have to have the leaders try to act it out in the WoW. otherwise some MMO players will yell that this screws them over, they would loose players, and ultimatly either one game or the other would be ruined because they have to dovetail them to work with eachother, meaning that they either have to have an enormus patch, or the game itself would have to have a design change to represent the different world that the players are in.