It should be backwards. It is the wizard's power the one that is artificial. I'm growing more and more tired of portraying sorcerers as "the wrong way to do magic".
Defilers are one of the things that would require some extra thought if converting Dark Sun to 5e.
Back in 2e, defiler was a separate class, and preserver was the "regular" wizard class. Defilers had two primary differences compared to preservers:
1. When they cast a spell, they drained the life from nearby vegetation which created a circle of ash around them, the size of which depended on terrain and spell level. In the revised version, this was changed to draining when memorizing, and gave them a chance to have fewer or more spell slots available that day, but that was a terrible change.
2. They had a much faster XP table, so at the same XP total as a preserver they'd be up to three levels ahead.
(Aside: The late-comer sourcebook Defilers & Preservers also added some BS about defilers following the "Path Sinister" which made Conjuration/Summoning and Necromancy spells easier to learn, and preservers following the "Path Dexter" which was better at learning Abjuration and IIRC Divination. That never sat well with me, because I always thought the evil of the defilers was expressed through the choice of defiling, and I also didn't think preserving was inherently good - you may very well choose to be a preserver because you realize it's not a good idea to crap where you eat.)
But ever since 3e, all classes have used the same XP table, with classes instead theoretically being balanced by way of what they get at each level. One may differ on how well they've managed to do that, but it's certainly the design goal. So, instead the defiler's greater power has to be expressed in some other way than higher level. Some ideas I've seen are:
1. Make defiling a choice when actually casting a spell to increase its power. That's the method used in 4e, where IIRC "Defile" was an at-will power an arcane caster could use to reroll an attack roll with a spell (which in 5e would translate to either rerolling an attack or forcing an opponent to reroll a save). This has the advantage of being a persistent temptation for an arcane caster in times of desperation, but the disadvantage that it means casters aren't "locked into" being defilers.
2. Make it a permanent choice, preferably one where a preserver can decide to abandon preserving and turn to defiling instead. This would give some form of permanent benefit to the defiler, such as increased caster level or additional spell slots. This was, IIRC, the path chosen by the people making the semi-official 3e conversion at athas.org. I had some disagreement with the way they chose to do it because they put a lot of the defiler's power in feats you had to take, but I always saw defiling as being the
easy path, not requiring special training.
As for sorcerers in Dark Sun, I'm hesitant about allowing them. The main problem is that they don't fit into the setting's history. The "natural" method of having supernatural powers in Dark Sun are psionics. Arcane magic was a later addition, and one that required a lot of research to bring about. On the other hand, the deserts are full of weird mutant freaks, and I don't see why sorcerers couldn't be used to represent some of those. The setting would probably need a new sub-class for them though.
Because by definition, if you play D&D you are a part of the D&D Multiverse. That's why you have Fighters that can be Champions or Battlemasters, Wizards of seven different schools, Bards of valor and lore, you fight a specific type of orc, a specific type of goblin, you can face mind flayers and beholders etc. etc.
