The Lose 100% Focus on focus use debuff on pestilence is bugged. This might be connected to Stamina based Runes bug where the player loses 100% focus when using stamina based runes.
If you watch the video clip here ( Watch Lost 100% focus bug | Streamable ) you will notice that I lose focus even when I’m not using runes. The last hit of my gauntlets is similar to the Front Flip kick rune that uses stamina.
The game thinks I’m still using a rune attack at the end of my gauntlet’s attack animation.