After having problems setting up addons to track my damage buff to the Twilight Tormentor morph I discovered something that looks rather unecessary and a lot like a bug. Normally when you apply a buff the buff gets active with it's full duration, lets say 15 seconds. Once the buff has 5 seconds left of it's duration and you descide to re-apply it. The buff will get overwriten and return to the same buff with a 15 seconds duration.The 5 second duration left buff will no longer exist but an exact identical buff with 15 seconds duration will now have taken it's place.

That is the case for all buffs I've found so far but the Twilight Tormentor buff. The Twilight Tormentor buff does not override it's previous buff but instead adds a new exact identical buff leaving you with 2x identical buffs. This makes it hard for addons to keep track of the remaining duration for the Twilight Tormentor buff and also creates a lot of unecesarry buff icons on your screen (ZoS standard buff settings)
This image displays the visual problem of the bug. (normaly I do not use ZoS standard buff system but for this screen shot it was necessary)