But from a statistical standpoint, they are first line players, so unless you know better than everyone else, they are first liners.
Of course durability means something, but it needs to be put in context. Kreider's durability issues have almost always been essentially meaningless games. I'm pretty sure he's never missed a playoff game. The last 5 or so seasons, we could make the playoffs with half a team, we were that good. The durability issues you are trying to claim for Zibanejad and Buchnevich the last two seasons haven't effected the team either. We made the playoffs easily last season with their injuries. This season, I don't think we are a playoff team, whether they get injured or not. You can claim durability issues, but if you put it in context, they play the important games, and when they are fit, they are first line players.
Kreider is not inconsistent. This is such a myth. He's as consistent in his play as just about any player who is around his level of hockey player. Some expect him to be superman because he's strong and fast, but that ignores his hockey skill-set. He's not Mario Lemieux, he doesn't have that talent. He has a lot of talent, but the difference between Kreider scoring 60 per 82 games and 100 per 82 games is not inconsistency, its talent he doesn't have. Stepan and Brassard are not on this team anymore, there's no need to compare them to Zibanejad. Your last point makes no sense. You are giving an opinion, not facts. We are talking about basic stats, not fancy stats. I watch the games.