There is a certain tension between the following two positions.
1) Save-or-die should be in the game because it adds tension and drama.
and,
2) Players should always be able to figure out when they are about to encounter a save-or-die, and it is in their own fault if they have not prepared the proper counter magic to negate it.
This is the worst of both worlds. You've got the potential for instant, random character death. In random encounters, that's just annoying. And in climactic encounters, the players know it is coming, and cast Death Ward (or Protection from Evil, or whatever is relevant to the particular save-or-die), and entirely negate the save-or-die effect. The tension is completely erased, as is the chance for character death.
So in non climactic encounters, my character could randomly die, and in climactic encounters, he won't because we know those are coming and we cast the "my character can't randomly die now" spell. Great.
1) Save-or-die should be in the game because it adds tension and drama.
and,
2) Players should always be able to figure out when they are about to encounter a save-or-die, and it is in their own fault if they have not prepared the proper counter magic to negate it.
This is the worst of both worlds. You've got the potential for instant, random character death. In random encounters, that's just annoying. And in climactic encounters, the players know it is coming, and cast Death Ward (or Protection from Evil, or whatever is relevant to the particular save-or-die), and entirely negate the save-or-die effect. The tension is completely erased, as is the chance for character death.
So in non climactic encounters, my character could randomly die, and in climactic encounters, he won't because we know those are coming and we cast the "my character can't randomly die now" spell. Great.