I've been trying Poppy again today and it just reminded me of the stupidity that is Poppy's passive. I like the shield part, obviously, but the fact that the Buckler drops in a random location bothers me. I would much rather see it return to her and shield her every time, but the shield strength would be reduced when it doesn't kill the enemy unit. This way you avoid the damn rng aspect of it, which shouldn't even be a thing with her.
TL;DR: Make the Buckler return to her at all times, but reduce the strength of the shield when it doesn't kill the enemy unit.