What I love/get really amazingly frustrated about is that the Scorpion are not the most honorable by a long shot. They have convinced enough people how useful they are, but they have, in fact, always acted in self-interest. It's an amazing con that has persisted for centuries. If you read through the history you'll find that they have failed as the Empire's spymasters in huge ways, often suspiciously. The Tortoise clan were formed solely to do the kind of work the Scorpion are supposed to do, working for the emperor directly.
Even among the clans, the Scorpion are not trusted enough to be of use. The Crab let the Yasuki family handle their less samurai worthy tasks, and the Kuni are certainly willing to get their hands dirty as well. Also, if you read the kind of stuff the Kuni did to learn about the Taint, those were some horrible, tortuous deaths. The Unicorn and Mantis both rely on foreign entities to do their dirty work.
The Phoenix, Crane, and Lion (presumably) have made some use of the Scorpion clan's talents, though the only one that comes to mind was the entrusting of the Black Scrolls (which the Scorpion sold). The Dragon seem to be the only clan that really value the Scorpion, which is because the Scorpion know better than to double cross them. Unlike the other clans, the Dragon can see past their bullshit. So the Scorpion come through for Dragon at every opportunity, which does two things for the Scorpion. First, it keeps their biggest threat off their backs, and second, it allows them to tell the other clans that they are loyal to "true friends," leading to the other clans and individuals to seek their favor.
In short, the Scorpion are every bit as bad as you might suspect. Their apparent honor is the best-written con I've read, but is nothing more than that.