They changed the signet trait because they were mindlessly following their balance philosophy of no cool-down reduction traits instead of considering that sometimes it's best not to follow the rule 100% of the time. I think it was a huge mistake because the old trait made signet passives stronger which Vampirism Signet needed to be viable and more interesting. Also, when you consider that you probably won't be running more than 2 signets at a time that trait simply isn't worth taking for an extra boon ripped every 24-30 seconds.