Just an observation:

Thri-Kreen (Dark Sun): Natural AC 5, unable to wear armor or accessories.

Faerie (Wizardry 6-8, some Japanese Wizardry spin-offs (including Elminage Gothic): Natural AC 5, extremely limited equipment selection.

I just noticed this similarity.

(There is one significant difference: Thri-Kreen make decent fighters with their natural attacks, while Fairies tend to be more oriented towards fast magic use.)

Now we just need a Half-Dragon race that would get a breath weapon like the one that Dracons get in Wizardry.

Thri_Kreen, when properly built, are pretty OP in Dark Sun. Their weaknesses are not exploitable in the Dark Sun games (i.e. their hive-mind mentality and dedication to 'The Hunt') Their limited gear selection does not absolve the fact that they get four attacks per round and make very good psionicists.

There are "half-dragons" in Dark Sun...they are called Sorcerer Kings...the bad guys. All of the Sorcerer Kings are trying to become a "dragon." Naturally, they are NOT playable and are stupid-powerful. In fact, the transition between Dark Sun 2nd Ed and Revised 2nd Edition was the death of one of the Sorcerer Kings before his transformation (Kalak of Tyr) and the big jump after that was the destruction of the Dragon of Tyr (Borys of Ur Draxa). Dark Sun 4th Edition does NOT do Dark Sun or Athas justice.

Agreed that Thri-kreen can be extremely potent if built properly. You DEFINITELY want to make them a Psionicist, because a lot of the powers in the Psychometabolism line synergize really well with Thri-kreen. You can get maximum usage out of their multiple attacks by buffing them with Enhanced Strength (or, if you're playing WotR and have a max Strength Half-Giant in the party, with the Cleric spell Strength of One), and Animal Affinity. And of course, throw on a Haste from your Preserver while you're at it.

The biggest drawback is that none of the Thri-kreen's attacks count as magical weapons, so there are some areas in both games where you'll need to give your Thri-kreen some magic weapons or they'll be totally useless in fights.

A Thri-kreen's AC can also be shored up through use of the Psychometabolism powers Biofeedback, Displacement and Flesh Armor. When combined with a shield, you can get their AC to -9 or -10, although using all of those powers drains your PSP very quickly, so I recommend only doing this for tough fights.