Here's what I've found on Dark Sun's classes (source is 1d4chan):
- Clerics - There are no real gods in the setting (according to 4e, this is because the Primordials drove them off in the Dawn War), so most clerics worship elements or quasi-elements. In a desert world, summoning water elementals will get you * until you realize that if you level up to much you become a true elemental too. Very nasty to be drank alive for being a water elemental. The way they are described, they are more "elemental shamans" than archetypical clerics. Other types are insinuated to exist, such as a 'sun cleric' featured in the novels, representing the aspect and domain of the sun as a natural force rather than a deity.
- Druids - Druids serve spirits of the land. They have a guarded lands that they are responsible to look after.
- Gladiators - You know. Like the movie. Also one of the most overpowered classes in the times of AD&D, a low level gladiator could be the personification of a certain Frank Frazzeta illustration entitled "The Destroyer". Essentially, they were Barbarians before Barbarians as 3e made them were a thing.
- Dune Traders - lol that's actually a class? Was more one the role-playing side of things, could get loads of handy contacts and power within tradehouses. Took care of diplomacy, trading, and generally any situation that could be resolved without a weapon.
- Fighters - Not as good as a Gladiator in personal combat, but who is? Really excelled at attracting and leading armies at higher levels.
- Bards - Most bards sing songs and boost the other party members' rolls. Dark Sun bards will poison and kill you, and maybe **** you. Maybe in that order, too.
- Paladins - lol nope. Honor and virtue fell by the wayside a long time ago on Athas, but what else would you expect from a planet this Darwinian?
- Templars - Replace Paladins thematically, but more on the police side of things to the point they are like the Gestapo in the French State. Ability-wise, they're more like Clerics with slower spell-progression but more spellslots and the ability to use any weapon. Worship the Sorcerer King who rules their city.
- Psionicists - Psionicists are considered accepted and normal in this setting. In fact, every PC is guaranteed to have at least one psionic power! OMGWTF! Think Jedis, kind of. Wanna move naughty word with your mind without casting a spell like some faggy ass wizard? Check. Mind****? Check. ****ing Time Travel? Double Check. Unfortunately suffered from the fact that psionics in 2e were a horrible mess, and with a few notable exceptions, most of your powers are either incredibly niche or use clunky subsystems.
- Rangers - Same old ****. Think Aragorn in the desert.
- Rogues - Pretty similar to the non-Athasian kind. Attracted a Patron at level 10, aka you work for me now bitch.
- Wizards- Two types exist in the setting, but everyone hates them both:
- Defiler - Evil mages, who suck out the life force of things. When they level up enough, they usually have an allergic reaction called dragon metamorphosis.
- Preserver - Mages who are not manly enough to steal life force, so they sacrifice efficiency to keep the stuff around them alive. Unfortunately for them, the commoners think all wizards are the same. Fortunately for them, most of their naughty word can be passed off as psionics. When they grow up enough to be considered bad ass they turn into the manta ray like aliens from Abyss.
I think these could be restructured to a certain extent, making Templars the Cleric subclass, Defiler the Wizard subclass, Preserver the Sorcerer subclass, Gladiators the Barbarian subclass. Maybe cut Warlocks, even though I think Rajaat and the new dragons could all work as patrons.