While I do like the ability of that this card can do... just somehow feel there is a missmatch of the theme.
Since a Reaper usually is about death, and less of poison. (yes, I know, cause its the current mechanic that work well as a DoT)
Could maybe rename it to something like Poison/Foul/Plague Zombie/Rat or something.
Alternatively, could keep it as a reaper, but introduce a new mechanic (like Curse, where a Curse 2 would mean its ATK -2, and take 2 HP damage each turn, etc)
Just some minor thoughts...