Mercy finishers are prevented by proc animations and ragdolls.

[Kainosh]

If enemy is ragdolled or playing proc animation, Mercy can't be initiated.   That makes Mercy pretty useless, and quite often enemies die during these animations.

This issue was reported already.....I just wanna remind you guys that it is still not fixed.

 

Mercy kill must pull enemies out of any animation, state or ability.   Otherwise it should not be called "mercy"....

 

[Quimoth]

Noticed the same, you got my vote. The current system makes mercy kills even more wonky.