What are the Classes FOR?

[Skandranon]

WARRIOR: main tank.  This is the classical tank archetype and it does the job.  Clearly Blizzard's intention.

Yes.

Warriors are excellent party leaders and can control the pace all by themselves.

No. True before MC and 40-man raids, false afterwards.

Or rather, if your warriors are controlling the pace there's an issue. Pulling with warriors in 40 man raids is highly inadvisable. Their job is to lock mobs down, period.

PRIEST: main healer/debuffer.  Blizzard did a good job of making the Priest the "best" overall healer, but by a slim enough margin that other healing classes are not marginalized.  This was clearly their intention - to avoid there being only one healing solution in the game.  Else, they would have given Priests the ability to cure poisons, remove curses, and resurrect in combat.

Agree. Priests are obviously excellent healers, but not massively superior.

DRUID: secondary healer.  I still don't have enough Druid experience to determine if it's the un-viability of non-healing Druids that forces them into the healing role end-game, or simply because since they can heal pretty well it's what people want them to do because there's always a shortage of healers.  Ever see a bear or cat form Druid in raids?

I think secondary healer detracts somewhat from the druid's role. Yes, they are not priests, but they are definitely primary healers. As for the rest of their capabilities, I will not leak a strat, but there will come a time when one might not want to forget the druid's ability to go bearform. Also: innervate.

PALADIN: secondary healer/buffer/debuffer.

Unfortunately, yes. Not to say that they don't do it decently well, but most people who play pallies didn't sign up for this.

HUNTER: ...DPS?  Something tells me that Blizzard never quite had a handle on this class.

Your commentary is mostly accurate for instances up to UBRS and not accurate for 40 man raid zones. I know myself how hard it was to believe that hunters were supposed to be "the best puller" before I entered MC. But there's nothing like MC to demonstrate the pure capability of a hunter with enough skill.

Hunters are the best pullers in the game. Feign, disengage, distracting shot, and eyes of the beast give them the ability to pull mobs in whatever combination they choose, and multiple hunters working in concert can turn even the messiest groups into an orderly series of small, controlled fights. The upcoming Wyvern Sting will only add to this incredibly critical ability.

Oh yeah. Highest/second highest sustained ranged DPS.

MAGE: AE damage king/crowd control.  Not the ultimate single-target damager, which deservedly belongs to classes that have to get up close and personal to do damage; however, against multiple targets, the Mage rules.

Mages, right now, are quite weak in the end game. The fact that the majority of the boss fights in MC would probably go smoother if you brought zero mages is just one of the points. I'm not arguing the capability of the mage, exactly, so much as the fact that the way the end game encounters are designed massively marginalizes the mage's best points.

Polymorph, one of the things people point to as powerful for a mage, is one such point. Before raid instances, polymorph is gold. Refreshable, ranged, long-term CC. However, in MC, poly is useless in all trash pulls and useful in one out of ten boss fights. It's slightly handier in Blackwing Lair, but not that much.

AoE damage, the other area of mage specialization, is of similarly limited application. Onyxia whelps. Flame Imps. Core hound packs. Firelords. These are it for when you might want AoE damage, and you don't actually need AoE damage for at least two of those four situations - it's just something for the mages to do while they're there.

A good ninety percent of a mage's time is spent pressing one button. On most pulls the button is either frostbolt or arcane missiles. On cursing bosses the button is Remove Lesser Curse. When mages are doing damage, they're doing a) the least/second-least damage of all damage-dealing classes, and doing it B) in the least efficient manner of all damage-dealing classes. And when they're decursing, they're no better than druids - actually, druids are better since they bring innervates and extra healing.

WARLOCK: DPS/utility.  Warlocks have so much utility it's crazy. 

Most powerful PvE class in the game, bar none. Again, this is partly a mix of capability and encounter design. Whereas everything in MC is immune to Polymorph, a great many targets are susceptible to Banish. The Warlock's highest-damage attack spell, Shadowbolt, is also not naturally highly resisted like the mage's highest-damage attack spell, Fireball. Along with the curse, you find excellent sustainability and a damage rate that surpasses every class but rogues.

Healthstones, soulstones, summons...the rest you've all heard before.