Playing  on  iPhone  XS.  iOS  15.1

I  notice  this  problem in  Arena  most,  but  it  has  happened  in  dungeons as  well.  Zargal's  devastate skill  is  supposed  to  active  her  crack  armor  skill  when  the  devastate  skill  kills  an  enemy.  This  doesnt  always  occur.   

Most  revently,  on  December 2nd,  i  was  in  arena  battle  against  player  named  natassoul.  enemy  team  was  Siphi  the  loat  bride,  apothacary,  gorgorab,  and  crimson  helm.  My  team  was  miscreated  monster,  Zargala,  visix,  and  Scyl  of  the  drakes.  I  killed  gorgorab  with  Zargal's  devastate  skill  and  nothing  happened.  Crack  armor  skill  never  activated