I think it's counter-productive to keep a player who's not ready to produce offensively no matter the context.
He's going to play less because he's not ready to play against big lines from a defensive standpoint and doesn't have the offense to offset it, and his confidence suffers because he's not producing. In the end, the only thing Slaf learned is what are his flaws in the NHL.
The only time it's a good decision it's when the player can produce and needs to develop his all around game.
I think it would have been counter-productive to have him in the the AHL because he would have learnt nothing about the NHL game. There is no substitute for NHL ice time and practices.
I think he may gain more from playing 10 min on the 4th line in the NHL than he would playing 1st line in the AHL.
I think confidence comes before success. I don't think his production or impact in the NHL has any effect in his confidence level. I don't think he would have gained confidence dominating the WJC or the AHL. Confidence is not, and should not be the by-product of performance. Its the opposite.
I think Slaf learned way much more than only what his flaws were. I think he learned about a new environment, rink size, processing of the game, speed of the game, the routine and training of a professional, combined with all the games, etc.
Things he would not have learned in any other caliber.