Do you have any examples of games where you can't abuse the system?
DA:O - had a character who, when buffed, was hit maybe 2 times while fighting against a revenant because his defence rating was so high.
BG2 - Many dual-class characters can easily solo the game (and the game has a max of 6 player characters, not 4). End boss (and also the imprisoned one) can be killed as soon as they spawn.
etc.
Games have to be accessible to many playstyles to have as wide a paying audience as possible.
It's easy to make overpowered characters in just about every roleplaying game. In order to have fun if you're at the skill level where you find things difficult you tend to need to 'gimp' yourself.
A much harder difficulty level would, however, be very appreciated.
