This last chapter didn't really make sense in context with what we've been shown in the manga. So far, THE has one every dual they've been in, including one involving Stern, the top ranked player in the game. However, in these duals they were unilaterally crushed and there opponents were being supported by those sprite things, which have been shown to be less than competent.
That would make some sense if they had a more rocky record or weren't already beating the top teams and players, but that's not the case.
Also, how is itemization and leveling supposed to work in this game? Nanoha as a brand new player overpowered Stern as the top-ranked player who's been in it since the beta. In most games, that should be numerically impossible based on gear alone.