Actually, its rather smart of them not to display success rate.

Imagine the cries of a broken system should they display say, a 90% success rate, when QS'ing only 78 items are crafted successfully. That's well within the realm of the possible (its possible that there are no successes, albeit extremely improbable) but would be taken by too many with little to no knowledge of probability as a sign the system was broken. They'd be happy with 92 successes, but unhappy with anything less than the 90 listed - or whatever the listed success rate would be.