Warrior DPS performance is tied to how well you time your CDs. You want your CDs active for their full duration and expire when the boss dies. This leads to maximize the execute phase DPS.
The weakaura displays a CD icon when the boss your are fighting drops below a custom health % threshold.
It is required to setup your own timers in the Custom options tab.
Tip: Go to warcraftlogs and use the filters in the 3rd screenshot to calculate the boss health % X-seconds before the combat ends. X-seconds refers to your CD duration (30 seconds for Deathwish).
This weakaura is included in the collection: https://wago.io/nu37vKWEn