This weakaura will show you when the MASTERY buff is up and only the MASTERY buff. It will also only show when your trinket is off cooldown. It will also show you the duration of your buff when you use it. It also will only load in combat.
My other versions of this weakaura for the other buffs.
https://wago.io/WfXsuuxFk -Versatility
https://wago.io/8KmZEukDY - Crit
https://wago.io/WfXsuuxFk - Haste