While _some_ scale more than others, there are AP nukers (Annie, Anivia, and even Kennen) that can absolutely trash a hero lategame -- this is simply not the case with Pyromancer, who against a carry with max gear just gets eaten alive, and only serves to throw out the stun.
LoL overall has almost every archetype scaling well into the endgame, while in HoN auto-attacking heroes will eventually rule the field, leaving supports to clutch stun / tablet someone around.