Well.. The first Kazekage brought together all the clans who lived in the desert together in one village. It's only logical that in the middle of a dessert not that many people/clans lived in the first place. So therefor their numbers aren't too big + not many special clans.
Also: In a desert not many techniques can be learned as in other area's .. Suiton jutsu which need a watersource / Real doton with excisting earth is hard as well because it's 99% sand, jutsu concerning tree's and surroundings etc .. = that's why they have to many Fuuton users.. because the wind blows pretty much all the time there...
on a sidenote; almost every Kazekage has got assasinated .. (don't know about the first/second) but the third, the fourth, even Gaara...
+ Some very strong ninja leaving the village.. : Sasori is a best example
The hidden sand has had some splendid Shinobi for sure.. but they have a small population (because of living in the desert) so they stand out less then other villages with large populations like Konoha, kumo, etc..
Extremely strong known Hidden Sand shinobi: 1st kazekage, 2nd Kazekage, 3th Kazekage, Gaara, 4th Kazekage, Chiyo, Scorch style girl, Sasori, Baki, Temari, Kankuro, the creator of puppet jutsu, etc ...