In my discussion of the classes for Dark Sun 4e, I stated that the Sorcerer class is a bit of a problem mainly from the fact that fluff text and neither of the builds are a good match for the setting. Here is a slightly modified class build that fits better with the magic source on Athas.
You have always been able to feel the vitality of the material around you but now you have learned to harness it and bend it to your will for spectacular affect.
Vitality Pull: Your feel for the lifeforce around you allows you to better harness it for arcane affects. You gain bonus to the damage of your arcane powers equal to your Wisdom modifier. This bonus increases by +2 at 11th level and +4 at 21st level.
Vitality Sense: Your feel for the lifeforce around you allows you to anticipate attacks. While not wearing heavy armor you can use your wisdom modifier in place of your Dexterity or Intelligence modifier to determine your AC.
Protect Vitality: You innate feel for vitality allows you to protect yours from attack. You gain resist 5 to Necrotic damage. The resistance increases 10 at 11th level and 15 at 21st level. This resistance works against damage caused by defiling magic.
Absorb Vitality: Sometimes you pull in to much lifeforce to drive for your arcane power. You have learned how to absorb this into yourself. While you cannot hold it forever it can add a boost to your vitality. When you roll a natural 20 for an arcane attack you immediately gain Wisdom modifier temporary hit points.
Find Hidden Vitality: Your natural sense allows you to find hidden sources of lifeforce to power your magic. The first encounter power you use in any encounter does not count against its use for the encounter(ie the first encounter power you use can be used again in the same encounter).
Design Notes: These are mainly based on the existing Sorcerer build features with the Find Hidden Vitality to compensate for the fact that I was not interested in writing powers for every level which give a bonus like you get with Dragon Magic and Wild Magic Class feature. The necrotic damage protection makes this class good for defilers working in groups or people hunting defilers if you use a more rational defiler/preserving rule.