Soul Reaper should shine at target 35% (or 45% if T15 4p bonus present) indicating that it will provide with the bonus shadow damage show the self haste buff gained if the target dies within the 5s window.

Currently it only shows the timing for the shadow damage tick.

http://www.wowhead.com/spell=130735

Been fooling around with github dafzor@8d1a793 think this might do it although Blizzard sparkle border would be preferable imo, no idea how to do it though

I have merged your commit. I prefer to use the "hint" effect for things AdiButtonAuras adds, to differentiate them from built-in Blizzard highlights.