Did Giroux deteriorate as a passer? Voracek? (as a shooter yes, you'd think that was an area of emphasis?), Couts?
I think Torts is right that offense is primarily instinctive, you can draw up plays but they quickly break down. There are some things that can be coached, like Briere and the analytics guy showing TK where he needed to be to score more goals. But Farabee showed his skill set before he was drafted, Brink was a great playmaker in college, G and Couts in the CHL.
The guys who fail to translate skills from lower levels I suspect are the ones who can't adjust to smaller windows and more physical play - it's more about revealing their limitations than failing to develop their offensive skill sets. This is probably more a scouting failure (failure to recognize flaws that will be exposed against better competition) than a development issue.
The primary failure with most offensive players isn't development, but not recognizing player strengths and weaknesses and putting them in positions to succeed. But in that case we should see players thrive elsewhere with smarter organizations that recognize their talent and given them better opportunities. The fact this hasn't happened suggests talent is the real problem.
Defense is much easier to coach, positioning, stick work, learning to use leverage in puck battles, understanding your responsibilities. Even then, IQ and effort really can't be coached, low motor guys might be motivated by fear in the short-run but will regress to their norm, and stupid players don't suddenly get smart.
