One of the important things to remember with animation is follow through, meaning, don't just animate an action, animate the character. Make sure to keep the character(s) moving at all times.
'Never a dull moment.'
I think you honestly need more wind up frames before it throws it, right now it looks more like it's waving it around rather than throwing it.
How I would do it is to have the sythe shoot up into the sky, and come twirling down into the reaper's hands.