Originally Posted by
Karbuncle
Most if not akl speculation would be unfounded, or placebo effects at work, unfortunately.
There is simply no tests on steal, considering in all likeliness the item stolen, and the mob, and your level all could play a part in it, so even if you go out and steal from the same mob 1000 times for a solid sample, it'll likely be different and moot for any other mob, which is why no ones bothered to try and build a reasonable formula for steal rate.
It would be a near impossible task, not entirely because of a 5 minute recast, and for such little payoff, its not worth the time of effort. Best advice is to equip your steal+ gear, for whatever little effect it may have.
So more or less, no ones tested it cause no one cares. Stealing items has never been worth a squat, and it usually takes no more than a handful of attempts for quest items (Test or AF stew stuff), so just equip your steal+ gear (WhichisprobablyasplaceboasTH+) and have at it.