Let me hear your ideas and critique
OK.
Let me say this up front: Dark Sun is my favorite setting of all time.
I never did get a chance to play DS using RM rules, though I have wanted to for a long time. RM is just a better fit, IMO, for the setting, particularly its supposed deadliness which never seemed to make an appearance when playing it with D&D rules. (Yes, I know they were AD&D 2nd edition, but that was less deadly than AD&D 1e, as HP bloat started there.) All of that is just to say that I never got a chance to really dig into the rules you put together, though I assume they are based on RM 2nd edition, and I have a moderate grasp of those. (I am more familiar with RMSS/FRP.) So I just took a glance at them (not the ones you just did, so you might have addressed these, if so, ignore) and noticed a couple of things:
Defilers. These spellcasters have a reason they are defilers other than just being bad. Sort of like the Dark Magic in The Dragon Prince on Netflix - I highly recommend it, and never knew I wanted Scottish sounding elves until that show - and the Dark Side of The Force in Star Wars, it has an element of ease to it that is seductive. I did not see anything in them to note that using defiling makes casting spells easier/quicker, which it should. I don't think it needs to make learning spell lists easier, but utilizing defiling methods for spellcasting should make casting spells - and maybe
overcasting - much faster. (Or possible, when talking about overcasting.) All the details of how much plant-life is destroyed is fine, though I would handwave it as a GM; too much trouble to bother with in game.
Psionics. I do not like these being handled like magic. Psionics should
feel different, for the player, and not just be said to be different. I get that the whole "Mentalism" school looks like an easy route to take, I just don't think it is the right one for DS psionics. Instead I say look to how they are handled in Spacemaster: Privateers. I think that could be used better to model the whole "Wild Talent" thing, as well.
May I ask for more detail on what you mean by: "revised spell-effects?" Are you asking if we think some spell effects should be altered?
Edit: Just downloaded it and will take a look over the weekend.