Interesting fact: Rick Nash hasn't played a full season with the Rangers. In his time here, he's scored at a 35 goal per 82 game pace. So, while you are right that he hasn't actually scored 30 goals, his regular season numbers are in line with his norm. Omitting his rookie year, his career pace pre-Rangers is 37 goals every 82 games. Goal-scoring wise, not much of a disappointment.
A problem though. His Columbus assist pace, again omitting rookie year, was 32 per 82. Over his last 5 years there, the pace was 35. In his two seasons here, that number is 25. Last year, the pro-rated full season number was 16. That, to me, is a mark of a goal-scorer who isn't making good decisions with the puck. He finds a way to keep scoring goals, because talent, but his overall offensive play has suffered. That statistic really bears out the eye test, too. In that sense, last season was a bitter disappointment, even before the playoffs began. Concussions can play a factor there, but he needs to be a better decision maker when he has the puck this year.