Right. So. Every once in a while some 'genius' will come up with some new way to 'fix' Shadow Word: Death. Really, there's nothing wrong with it in the first place, but it seems to offend people, just the same. I should explain that Shadow Word: Death is that rarity - an Instant Cast spell with very decent damage and a chance to crit. The 'balance' for all that goodness, however, is that, if the spell does not kill the target, the Priest that cast it takes shadow damage equal to what it did to the target.
Very soon after it came out Blizzard increased its cooldown by a bit, as it was ruled a bit over-powered AND made it's rebound damage unresistable (as Undead Priests have some innate Shadow Resistance). Some SPriests seem to never have gotten over the 'nerf'.
The most recent 'genius' seems to think that SPriests should get some sort of buff if we happen to manage the 'killing blow' on elite targets, as a 'balance' to the 'risk' of taking damage by casting it too soon.
Okay, first off, what SPriest is actually only casting this at the end of the fight? One either uses it in rotation, or one does not, for whatever reasons one has.
Second off, if I actually manage to get the 'killing blow' on an elite mob with Shadow Word: Death, forget some silly buff, I want fireworks.
Edit: And an angelic choir singing songs of praise. I mean really. An SPriest getting the 'killing blow' with SW:D? Ha!