DESTRO CLASSES:
Tanks- DESTRO Owns in tanks.
Chosen- INCREDIBLE PvE solo class. Can basically tank/grab 6 mobs 4-5 levels higher than them, and kill them easily while taking little to no damage. No other class can do that except other tanks when they are lvl 40ish
Black Orc- The Front Runner for competition in the OMG nerf me class. Black Orcs are uber uber instance tanks. They can Warhammer  the highest lvl bosses with a little skill and moderate gear. In fact, most Borcs wont run with another Borc in party cause it isn't needed (yet other parties need 2 tanks to finish a high lvl instance) and they dont wanna roll against someone in loot. They can negate virtually all melee damge coming in, and can also mitigate a crap-ton of magic damage as well. If geared right. Did I mention they also heal themselves, just by hitting people? lol

DPS: We are behind order here.
Marauder-- Uber class in t1. moderate in t2/t3, better than average again in t4. In t1 they are almost unstoppable, until BW get their DOTs. And even then a Marauder will usually roll in an SC
WE-- Meh. Supposedly they are the uber BW killer (and thus in high demand), but in actuality it doesnt work that way. The theory goes, (stealth, appraoch back lines, Heal debuff, magic debuff, Big DPS, break root with yer abilities etc). Problem is, lvl 40s can see through the vast majority (if not all) people's stealth. my BW sees them coming from a mile away, as does my shaman (pertaining to WH). They can lay the smack down, but are Warhammer Gold  DOTted to death in under 3 seconds.
Squig herder--Sucked Donkey gutz until recently. They have been getting stealth buffs (i.e. not published widely in patch notes) and are becoming viable, Many people think in the 1.6 patch they will be insane, which is why lots of squigs are coming through t1-t3 now.) Their Spike Squg is invaluable in most instance runs.
Sorceress- Meh. Good AOE, moderate burst, moderate DOTs. Mediocre toon at best.
Magus- HORRRRRRIIIBLE to level up. But as u increase your power grows exponentially and u get the beloved vaccuum. There are very very very few people playing a magus yet they keep getting nerfed, not sure why, but maybe on some servers Magus are dominating. I doubt it though.

Healers--ROFL. what a horrible class to play. Don't DO IT. You have been warned. lol
Disciple of Khaine-- Probably the very best class to Solo a mob in PvE. or even solo in RvR as well. At lvl 33 you can solo a 35 hero. at 36 you can solo a 40 hero. in your 20s you can solo 2 champs your level or slightly higher. Can any other class do that? not that I know of. Of course u may need to use about 75 silver in pots to take on that 40 hero, but still.... 75 silver? lol. I make that in 2 minutes. maybe less.
Shaman-- The most popular healer on Destro. Many people Warhammer Gold into the "Ranged DPS/Healer" garbage. In actualitly we are a very very very weak Ranged DPS, with moderate heals. We have great range on our DPS (woohoo, thanks). And our HOTs are good. But we get one "big heal" (i.e not HOT) and it is on a 3s cast, and it is interrupted just by you blinking let alone being hit (ok slight exaggeration but not by much). It takes about 7-10 seconds to cast this spell in RvR, during that time your party is dead. They suck
Zealot-- Best healer on Destro side. But that aint saying much. If it isn't bad enough that their heals dont compare to a RP, factor in that they level even slower than a Shaman (if that is even humanly possible). Thus, almost NO ONE plays Zealots at high lvl.