Monk is the worst offender.
People saying you can play a monk without better ability scores than other characters ... wrong.
Then saying that you just "can't play it like a Fighter or Rogue" ... wrong.
What should a Monk DO? If you're saying they shouldn't do anything, then, what's the point of the class?
A Monk with poor STR ... you get the lottery effect, but the biggest problem is that half their bonus feats and special abilities are STR based. What possible use is it to have Improved Trip if you can't actually TRIP anybody once you're there? What use is it to have Improved Grapple if you can't win any grapple opposed rolls? If Trip and Grapple allowed monks to sub Dex in, then they could dump STR totally, but they can't so you can't. Stunning Fist and Quivering Palm require you to HIT, which unless you're going Finesse and avoiding the Improved line totally, means you're SOL there as well.
Monks need Dex for AC, because they don't wear armor. They can go Finesse and make Dex more important by subbing in this stat on the To-Hit, but standard you're not there.
Monks NEED Wis because it replaces their ability to wear armor. Bracers of Armor are artificially price-jumped. A Dex-based character of another class can grab the ever-present Chain Shirt and Mithril Chain Shirt for cheap, and enchant it for even more cheap, but the prohibition against ALL armors really shafts the Monk there. To get even the AC of a backline archer, then, the Monk has to have a 16 Wis (+3, +1 Monk) to START OFF ... but the monk doesn't have any ranged abilities, so he has to get in and mix it up.
The Monk is also a high skill-point class with skill-dependant abilities. He has Move Silently, Balance, and Tumble for doing rogue-like things. So he needs at least passable Int to keep ranks in those. To say that the ROGUE should be the only one using those skills is missing the point. The rogue isn't the only light class in the game, the rogue is the only trap-disarming class in the game. Monks and Rangers also get in on the silent action.
You can, of course, take all of those things away from the Monk, and really then, why's the guy playing him at the table anyway? The monk is there to mix it up in melee, sneak around, and use special close combat feats. Nobody expects him to disarm traps for the rogue, nobody expects him to do more damage than the barbarian, nobody expects him to tank like the fighter. But he has to do SOME of EACH of those or there's no point in playing the character. And if he can't effectively DO any of those things, then it's a bust class.
I sigh every time somebody wants to play a Monk. I even allow Monks access to some extra non-core feats to give them a leg up, but the fact remains that with point buy set any lower than 32, you can't keep up with the other classes even doing "your own thing".
--fje