I am not sure if this has happened to anyone but it seems that exterminate sometimes bug out from the 2 set pieces. If the extra stack of exterminate from the set is not consumed before the Reaper’s mark exploding then we sometimes only have a total of 2 exteriminate stacks instead of 3 stacks from the 2 piece tier set. Note: I am not sure if it is a bug with the 2 piece tier set or just something else altogether.