[Death Knight][Unholy] Defile mastery double dip

[Daggerinhead]

WoW Freakz spell link: https://www.wow-freakz.com/spells.php?spell=152280&&name=defile
Bug description: Defile damage gets increased by mastery twice.
Proof: https://imgur.com/a/xICg3Ka
My dk has: 10566 attack power, 18% base mastery, 34.86% mastery with fully stacked defile, +5% to summons from hidden aura.
Because defile damages changes over time as mastery increases, im gonna focus on first and last tick.
Tooltip damage is: 10566*0.7*11*1.18*1.05=100802 damage
Therefore 1st tick should be 100802/11=9164
However its 10813. 10813/9164=1.18 which is multiplier from mastery.
Going on to last tick: Expected damage is 10566*0.7*1.3486*1.05=10474. According to tooltip it should be 115225/11=10475
In game it ticks for 14126. Again 14126/10474=1.3486 which is mastery multiplier.
Here comes the conclustion that defile benefits from mastery twice, which shouldn't happen.

[Plaguesynth]

Confirmed . Been trying to find the issue myself but never thought of mastery being a doubledip on it , nice one .