So I just finished an ARAM as Sion, and I had a hexdrinker. It was on cooldown when I died, but then procced and shielded me while I was in passive/zombie mode. Not sure if it's a bug, but it's pretty lame no matter what. Shouldn't be wasting cooldowns that do nothing for the player, makes no sense.
Edit: It did come back off cooldown just after dying and entering passive. It was not up before passive started.
Incidentally, this also happens to Morde's ghosts. They'll happily proc hexdrinker for the ghost and waste it for the player, given the chance. So it's not only this after-death ability that does this.
You took magic damage while low so hexdrinker shielded it. It also helps, since it helps you stay alive longer while undead. Seems to be working as intended. Going from this, Banshee's Veil should also still be active if you died while it was up (unlikely, you'd have to die from non-spells only).
