I find it strange when you said Hernandez is not a poacher. I taught this was common knowledge, but then I realized that the way you define him as not a poacher is wrong. Rather than saying he has become more involved in our game as your defense, a better analysis would say his off the ball running and the ability to make teams play a deeper line sort of make him more than just a poacher.
Nevertheless, the fulcrum of his game is that of a poacher. The article below can help you understand better: (in particular the part that states why he lack playing time)
http://thinkfootball.co.uk/archives/11755
In my point of view, his all round game has shown improvement this year as you stated, but that improvement is not significant enough for him to occupy several roles on the pitch. Nor is consistent enough to say that he has "expanded his game, to be involved everywhere on the pitch." Using recent example of teams that did not put pressure on our attacks and are void of fight are not the best example to use to make assessment on an individual attributes. Earlier on this season, Hernandez did not show this improvement aforementioned and as such, it exemplifies the consistency that I could not find in his game.
Hernandez most noted attributed are his predatory instinct in the box. His reading/anticipation of the game(be in the right place at the right time) and the ability to finish clean are all characteristic that defines a poacher. Other attribute like technical ability and/or hold up play are not his strong point. If he had showed consistency in regards to the latter, I may see him more than just a poacher, but the basis of his career has been establish by characteristic that are mostly poacher-esque.