If you want to throw out a bunch of things against him, you can't make the argument that those count, but playing time and line mates don't factor in just as much, if not more. And I'd definitely argue more. I think those are way more significant factors than the ones you named. Namestnikov and Spooner were traded for a reason. Spooner was essentially given away, Tampa Bay ripped us off swapping Miller for Namestnikov. Miller could compete for the title of the Rangers top forward, Namestnikov clearly cannot, whether he ends the season with some extra points due to being carried by Hart Trophy candidates or not.
If no one got injured and ice time and line mates were distributed evenly, I think we'd see some four way split this season between Zibanejad, Zuccarello, Kreider and Buchnevich for the points lead. Which player lead the team in points could really just be a matter of who has a good season and who doesn't. Who has a slightly higher SH% this season, and who doesn't. Unfortunately, three of those players have missed a significant amount of games and two get significantly less ice time than they should, along with problems in the line structure, as well.
And no, he hasn't been good recently. Its not unusual that players would tune out when the games no longer matter, but whether he's done that or not shouldn't mean we excuse Insane Alain for his poor coaching.