I know that that can happen. And even in Shadowrun that can happen. They shooters can roll low and the person being shot rolls really well on his defense roll and stages the damage down.
But it is not a guarantee and it should be a scary tense encounter that you have to think twice about.
In most DnD games I have played in crossbows are limited to a d6 or a d8 if its heavy. So a high level character with a lot of hitpoints can be shot with a lot of bolts and not die. If you make most city guardsmen third level they are not even going to be able to hit a high level character unless they crit.
So you start seeing these arrogant PCs thumbing their noses at the local guards because they know that they can't be hurt. The only solution the DM has then is to raise the guards level.
So power escalation starts making the arms race look tame in comparison.
I guess what I want is to see character become more competent but not become demigods where a lone fighter can wade through 100 orcs. A game where people tell of the legend of Bob the world's greatest swordsmen who never lost a fight but died because he grabbed the evil King and threw both of them off a cliff.
Hm, sounds as if high level D&D is not the game for you. The idea in D&D is that if the great hero is trying not to be hit by the mook guardsmen, he won't be hit/seriously injured by them. If you're using 3e, I'd suggest E6 or similar might be a good approach (and make the guards 3rd-4th level vs the 6th level PCs).
It is much less of a problem in 4e, in 4e if you want a world where the lone high-level Fighter cannot wade through 100 Orcs you can easily stat Orcs accordingly: Orc Raider 3rd level, Orc Veteran 8th level, Orc Elite 13th level, Orc Battle Champion 18th level; that works fine in 4e.
It's also possible to run 4e as an Heroic Tier (1st-10th level only) game, but even playing through Paragon (11th-20th) you can plausibly stat the Orcs as high level Minions, this lets them do lots of damage to high-level PCs but they die easily. Or stat them as a very high level Swarm that will kill the high level Fighter.
Personally I have no problem with a legendary hero being able to defeat 100 Orcs.