I"m not real crazy about seeing "save-or-die" being mitigated with "save-and-be-debuffed" effects. Hear my thinking on the matter.
The principal reason it's accepted that a save-or-die spell should be pretty worthless is their potential to short-change a cool encounter with the casting of a single spell in the first round of combat. Here's how I see save-or-dies being used in a manner that most would find acceptable:
1) To eliminate a mook--a monster that doesn't pose a major threat to the party individually, so it's probably part of a pack attack. Not a boss. Of course, at higher levels, even a mook can have too many hit points to be dropped by a charging fighter, so a save-or-die can come in handy.
2) To take down any monster, even a boss, after a few rounds of combat. No DM wants a potentially cool encounter to end unceremoniously, but they don't want them to drag on forever and they often don't really want the party to lose. A well-timed SoD can win the day.
So, here are some options for adjusting save-or-die effects in future books:
- Doesn't affect creatures beyond a certain number of hit dice--This makes an effective mook-killer, but bosses will usually have enough hit dice to put them out of danger of being one-shotted, and hit dice isn't something that can be reduced on the spot. I suspect many wouldn't even mind a no-save effect if it was restricted to killing minions.
- Hurst first, kills later. The spell's immediate effect is to do some no-save damage or imposes some other effect (like slowing), and forces a save on a subsequent round to avoid death. This is a lousy mook-killer, but can nail tough monsters.
- Only kills weak or hurt monsters. Power word kill already works this way, and it could work for other spells as well. The target has to be softened up first, which means the spell is reserved a sort of coup de grace.