Starfox
Hero
Dark Sun's real roots lie in Jack Vance's Dying Earth, which was clearly a huge inspiration for the setting (apocalyptic swords-and-sorcery world beneath a bloated and dying crimson sun). It would have done better to cut its ties with Tolkien altogether.
Beyond the sun and nearness of the end, I don't really see any similarity. Dying Earth is a decadent place full of indulgent people fighting boredom. Dark Sun is a half empty barbarian place, with the remnants fighting for survival.
To me Dark Sun is more like Gamma World in fantasy. Including mutants. Eberron is closer to Dying Earth than Dark Sun IMHO, but still way to energetic.
I do agree that Dark Sun could have used less nonhumans, tough.