It appears that the stat system is being radically changed for D3. This is not necessarily a bad thing, because the D2 stat system was far from perfect, but cutting the most fun part of Diablo (building your own unique character) in half is not, in my opinion, the way to do it.
WHAT WAS WRONG WITH THE D2 STAT SYSTEM:
Stats were ultimately useless except Vitality. The damage added to melee attacks by Strength was negligable, the impact Dexterity had on attack rating and defense laughable and the effect of Energy on your spells literally non-existent. The optimal stat distribution for EVERY character except Energy Shield sorcs was therefore: Whatever you need for the requirements on the items you're planning on wearing and the rest in Vitality.
The main problem observed by Blizzard was that it was indeed too easy to break your character. Since 90% of all characters put nearly all its points in Vitality and had high life, the game was balanced for characters with high life, and the result was that characters with any other stat build weren't cutting it in Hell difficulty.
I will not discuss the other problem (item design with stat requirements) here because I don't view it as a problem .
WHAT IS WRONG WITH THE D3 STAT SYSTEM:
There is none.
Oh, on paper there is, you just get assigned the stats automatically, but since there are no stat requirements anyway, you might as well not even have them at all and just give bonuses to attack rating, damage, mana and life based upon character level. These bonuses have always already existed on items anyway, so effectively, stats have been taken out of the game altogether.
EDIT: The lack of stat requirements on items means that every character can get the same items. Since some items are just better than others, this also means that many characters WILL get the same items, which is boring.
WHAT THE STAT SYSTEM SHOULD BE LIKE:
Stats should do something. A warrior who has been neglecting his Vitality in favour of higher Strength should do significantly more damage than the other warriors, the Energy stat should be replaced by Magic and actually affect the power of your spells, physical skills should have a stamina cost rather than a mana cost, and Dexterity should really be the deciding factor in your chance to hit. This way, players are less likely to mess up stat distribution because the system makes sense. If you distribute them in a way that makes sense intuitively - Strength for a fighter, Dexterity for a ranger, Magic for a caster - you will end up with a viable character.
But, and this is important: There is still ROOM for weird builds. If you want to make a caster with high physical stats and low Magic because you've found a spell that goes extremely well with melee attacks, you're able to do so.
In conclusion: There is a way to remove the flaws from the system without removing the system.