But those are the outliers anyway. In my longer running 3E campaigns maybe 5% of the total game time was spent at levels 1-3, and maybe 10% of the time was spent beyond level 12 and the other 85% of the campaign was spent at levels 4-12. During that so called “sweet spot” I never experienced characters getting taken from full hitpoints to -10 hitpoints from a monster crit. Yes, it’s theoretically possible for a fighter with a scythe to rip apart a pc, but when the rubber met the road at the game table what we wound up with were ogres and gnolls and gelatinous cubes and trolls and warriors with swords or axes and whatever else in the MM and PCs with full hitpoints didn't get one shot killed by a single monster's turn.
I've seen 5th-6th level 3e PCs killed by a single full attack from a troll, due to its Rend ability. I think that's the only sweet spot monster that does that, though. 3.0 Orcs with their 1d12+3/x3 great axes could easily one-shot 1st level PCs on a crit, of course.