Voss said:
And yet, the core feats are broken down into roughly three categories.
Really good ( natural spell, power attack, quicken spell, item creation)
Average (disarm, expertise)
and so incredibly bad as to be laughable (dodge, a lot of the dual skill feats)
Any subsystem that can range from extra actions to a measly +1 bonus is pretty much broken by default.
Well, if IIRC correctly, Monte Cook wrote that they did these things on purpose. The idea was to awared "Rules Mastery". Someone understanding the rules would knew that the 3.0 Skill Focus feat was worthless, and that Dodge was only useful as the "enabler" feat for other feats, but meaningless on its own. Unfortunately, this approach didn't turn out so great, because those people that "mastered" the rules quick enough disliked worthless abilities.
Then why to unbalanced feats and spells come out of WotC on a regular basis?
There are two factors to consider:
How many of the feats, spells and classes that WotC created are really unbalanced from the ones that they created as a whole?
How many of them required a combination of abilities from multiple source books?
And how many were intentionally created to be more powerful than what came before (The PHB II feats seem to fall into this area), and are thus a result of a change in the design guidelines behind them?
I don't know exact answers, but I assume that most "broken combos" require more than just one of the books, and are corner cases.
Their is also a difference of thoroughness in writing the core rulebooks or writing a supplement. In a core rulebook, the designers/developers basicaly know every part.* When writing a supplement, they typically have the core rules in mind, but how much they know about every splat book, regional source book or campaign setting varies greatly. Which means that combos obvious to those that own and use these books
*) there is still one problematic area: Sometimes, they don't remember the most current rule, but have an older variant in mind. That's why it is sometimes difficult to expect a designer to know the RAW, because for him, it's just one variant of the system... Let's just hope the designers will not be too confused