As for the Sharn Hardcover, I strongly disagree. A careful reading will reveal not one Psionic character, but about 6 to 8 of them. One of the most powerful individuals in the city is a Psion of 17th level! Psionics are also mentioned in relation to one of the Dragonmarked houses, and there is an entire page devoted to the district of Overlook and its Psionic population, including where one can find training and friendly faces in the district. A lot more than "one guy with a couple of levels."
Now, even with that, it's not a deluge of information, but remember that the majority of players do not use psionics, so every bit of psionic information is info they might find wasted. Proportionally to the amount of Psi-users in the gaming audience, they struck a pretty good balance I think.