an addon, which tracks the duration of debuffs on multiple targets at their name plate. Tidy Plates does this, but it's not perfect because the counter ain't that big and the icons fate as you switch target.
And a popular PvP addon, showing CDs underneath their name plate and the duration of running CDs above their name plate.
PlateBuffs is the addon used in the video. Platebuffs is a standalone addon that only adds the icons above the nameplates, the fading is controlled by the name plate addon.