I agree with you, but I think its a different issue to what I was discussing.However, suppose the Elf Wizard has a save bonus of +5 (very believable, if the Barbarian has a +12). He's still screwed on nothing but a twenty. You can fix it on the fly, but in 3.5 characters can have stats so widely divergent in the same group, with nothing but the core 3 books even, that a challenge for one party member is still certain death for all the others, making it hard to make a challenge that the whole group can share. You're going to have some difference between your wizards and your fighters, mind you, but you could have a seven to ten point gap between characters of even the same CLASS in 3e. It's one of the things that bugs me about 3.5 once play gets over 11th level or so.
If an NPC is optimised to target a PC's worst save then 3.5's "solution" is the Raise Dead spell.
As a DM, one of the things I am enjoying about War of the Burning Sky is that once the characters have completed the second adventure they basically get an "extra life"; the first attack each day that would leave them below -9 hit points instead stabilises them at -9.
There is an in-game reason for it in WotBS, but I'm seriously considering adopting it as a house rule for all my 3.5 games from now on.