I noticed two problems when using reaper:
1) when you go double reaper (leader+ friends leader) & you activate passive skill (with hp under 30%) animation appears only on friends reaper & not on my leader.
2) when i have passive skill activated (with hp under 30%) & use card with fixed dmg amount animation on reaper appears, but dmg is still fixed to its number, do not multiply.
Acording to 2nd problem there may be 2 ways to solve: 1) assuming that animation works let the reapers passive skill work with fixed dmg cards or 2) remove animation when we use cards with fixed dmg set. As for me i prefer solution number 1.