Thief’s skill Steal, has a recharge time of 35 seconds untraited.
Putting 30 points in the last traitline – Trickery, is supposed to reduce the recharge time by 30%. But it reduces it to 27 seconds. That is 20% reduction – 8 out of 35. The final trait from the same line reduces steal by 20%. When at 27 seconds recharge, I put this trait, the recharge time becomes 21,5 seconds. 20% of 27 is 5,4 so that is right. But 30% of 35 isn’t 8. The recharge time when having 30 points in the traitline and the final trait, should be 17,5 seconds. Last night the description was saying 17,5 seconds, but the actual recharge was 21,5 seconds. And today Arenanet made a “fix” to the description. But it is the effect of the traitline you should fix, not the description.
First screenshot: untraited Steal
Second screenshot: Steal with 30 points in Trickery
Third screnshot: Steal with 30 points in Trickery and Sleight of Hand trait Steal Trickery Sleight of Hand
The trait line does not reduce recharge time. It increases recharge rate. Only the trait reduces the recharge time. Increasing recharge rate and reducing recharge time has a similar effect but they are not the same.