I looked through several pages of the Forgotten Realms Campaign Setting Official Errata, and all the corrections I saw were of content rather than presentation and, though many were surely mistakes and oversights which could have been prevented, I'd be willing to bet that many were the result of the input of players who requested tweaks and refinements. I'd rather go through the hassle of adding errata to my rulebooks than do without the improvements.
In any case, the kind of thing that gets corrected in the errata isn't the kind of thing that an editor would necessarily be able to catch. The authors are supposed to know the system they're working within--an editor knows rules of grammar and fundamentals of style. As far as I can see, whoever edited the core rulebooks did pretty well--it's the authors who occasionally dropped the ball.
In any case, the kind of thing that gets corrected in the errata isn't the kind of thing that an editor would necessarily be able to catch. The authors are supposed to know the system they're working within--an editor knows rules of grammar and fundamentals of style. As far as I can see, whoever edited the core rulebooks did pretty well--it's the authors who occasionally dropped the ball.
