I was expressing an opinion based on conversations with pitchers who I have met. I said that this wasn't a scientific survey, and yes it is based merely on anectdotal first hand information. Your evidence is also anecdotal and none of it seems to be first hand information. Yes, you knew Sain, but how many pitchers told you that Sain straightened out their mechanical flaws. I was not making a blanket attack on the usefulness of MLB pitching coaches contrary to what you may be thinking. Yes, there are good, bad and average pitching coaches just like with everything else. However, it is my opinion that their value lies in areas other than spotting and correcting mechanical flaws, which at the MLB level is very hard to do especially with veterans. I don't buy into the notion of pitching gurus who can turn around pitchers careers. Yes, it happens at times, but not as often as people think IMO. Again, this is my opinion as I have stated over and over. I believe they make suggestions and try to help pitchers tinker all the the time, but rarely do they spot a mechanical flaw that turns a guy around. If there was a pitching coach who could do that, he'd be worth his weight in gold considering the importance of pitching and the Yankees would be collecting them like Free agents. There is no bidding war over pitching coaches.
As for Farrell, I do not think he is a very good pitching coach. I didn't see the results when he was with us nor at Toronto. Of recent Sox pitching coaches, I think Wallace was the bet. Again, just my opinion, but I have as much proof of my opinion as you do.
Edit: BTW, Norm Sherry was the backup catcher for the Dodgers when he helped out Koufax.