Quartz
Hero
How about applying non-proficiency penalties to damage as well as to hit? And only masterwork weapons or better can cause criticals?
So that orc commoner may well be wielding a longsword but since he's not proficient in it, not only does he attack at a penalty of -4 but he can never do maximum damage, (for a longsword 1d8-4, min 1) and can never manage a critical hit to boot. Group a few together and you'll have an encounter where the PCs wil get nickel-and-dimed but no-one will get dropped in one hit.
So that orc commoner may well be wielding a longsword but since he's not proficient in it, not only does he attack at a penalty of -4 but he can never do maximum damage, (for a longsword 1d8-4, min 1) and can never manage a critical hit to boot. Group a few together and you'll have an encounter where the PCs wil get nickel-and-dimed but no-one will get dropped in one hit.