Yes - but paladin is banned in Dark Sun contemporaneously when paladins existed in other settings. That’s how you know that paladins should not be allowed in a 3.5E Dark Sun game. As for these other classes, there is no guidance whatsoever.
In 4E, warlocks were templars. It was an interesting choice, and helped make templars different to clerics. Note that in 2E, templars were better than clerics in other settings. They were like super clerics.
The lore regarding sorcerers is flexible. All the bloodline stuff was suggested to be possibly rumour, possibly true. But sorcerers could just as easily be using will to power to access spontaneous arcane magic. That is certainly the case of the 3.5E warmage, who is trained to cast arcane magic spontaneously.
Is that arcanist that is being burnt at the stake right now a wizard, beguiler, sorcerer, warmage, or dread necromancer? No one knows. While there is mainstream hatred of arcane magic, there is surely a segment of the population that is sympathetic, otherwise there could be no Veiled Alliance or any mages not affiliated with the Sorcerer Monarchs at all.
Why should an arcanist like a dread necromancer threaten the verisimilitude of the setting? Its just a specialist of sorts in necromancy. Its not like it overturns the dichotomy of preserving and defiling, unlike some other things introduced at the very end of the 2E Dark Sun line
The people of Athas don’t care about your arcane specialization. They want you dead because you are destroying the lands that keep them fed. I can’t think of a single thing about the setting as presented in 2E that could be undermined by having variant arcanists present in the gameworld.