Quote Originally Posted by nightwyrm View Post
10% of PrCs are better than the base class(es) you're entering from or are crucial for certain builds.
~10-20% makes you no better or worse than what you're coming from.
The rest are worth less than the paper they're printed on.
This is about right. The vast majority of PrCs are mostly useless. A good chunk of the remainder are only usable as dips. Of whats left, most are reasonably balanced. A few are broken.

I believe this is more a result of a lack of balance on the part of WoTC than any actual strategy.