That's not really true.
January 15th on: 3 goals in 7 games
February: 8 goals in 13 games
April: 2 goals in 4 games
February was his 2nd highest goal scoring month. And his highest point scoring month.
There was really just one stretch in March where he didn't do much. 5 game pointless streak and 7 games with just an assist. Overall he only had 3 goals and 8 points in 15 games. His shooting percentage for the year was a ridiculous 13.8% but an equally ridiculous 4.8% in March.
14-15 is in many ways the opposite of this year. Especially the start. Nash undoubtedly played well but never seem to be controlling portions of the game but was very productive. This year he's been noticeable with generating chances but is... whats bigger than a snake? Anaconda bitten? Dragon bitten?
I like Nash but between his injuries and his production (or lack there of) never matching his play he can be infuriating at times.
I would probably look at the four goals in 10 games he had starting on Jan. 8th, half of which came in a game against Pittsburgh. For me that was when it really first started.
February featured 8 in 13 games, but it also featured half coming in a three game span to start the month.
From Feb. 22, is when it really hit the wall and became hot/cold. In 18 games that includes the last week of February and the entire month of March (nearly a quarter of the season), he managed 3 goals.
If we zoom out and look at a bigger picture, we that from Jan. 8th on, he scored 15 goals in 38 games, which on the surface looks good.
But then we dig a little deeper and we start to see some patterns. First, we that 10 of those goals came in 8 combined games, and the production came in clusters where he was "on." That means in the remaining 30 games where he wasn't "on" between Jan. 8th and March 31st, he scored 5 goals.
That trend only seemed to continue into the playoffs where his numbers were propped up by a few multiple point games, which balanced out more than few goose eggs in the remaining games. The following season he scored 1 goal in the entire month of October before scoring 7 in November.
Once again, the 7 looks pretty good on the surface until you start realize that 6 of those goals came in a 4 game hot streak, which also included a hat trick. Once again, in the remaining 8 games, he scored a grand total of 1 goal. December was a lot more of the same with half of his goal production coming in back-to-back games at the end of the month.
January of course featured zero goals. For the entire month. Half of his points also came in one game.
He missed all of February 2016, came back in March and scored 3 goals in his final 14 games. And par for the course, two of three goals came in a mini hot streak.
So for the 2015-2016 season, 8 of his 15 goals came in 6 combined games.
The pattern more or less continued into the 16-17 season, in which he'd had a 2 or 3 game stretch where he'd put up some goals and points, which would make his "overall" production seem at least okay. Heck 5 of his 23 goals on the season came in a stretch of 6 games at the end of March.
The of course takes us to this season, which is more of the same. The only two differences are that now it's more or less widely acknowledged that he is streaky as all hell, and his scoring clusters haven't been as long or as productive as they were in the past.
In summary:
For the second half of 14-15, he scored 5 goals in 30 games that weren't part of his surges.
In 15-16, he scored 7 goals in 52 non-surge games.
In 16-17, he scored 18 in 61 non-surge games.
So in a three year span, if he remove the games in which he looked he was playing video game hockey, he scored 30 goals in 142 other games. Or roughly a 15 goal in 71 game pace.
So in that sense, it really isn't a surprise to me that with increased age he's basically on a 17 goal pace, thanks in small part to shorter surges (such as nearly half of his goals coming in a three game spree from Nov. 11th to Nov. 15th).