Doesn't it seem like this arc has some really short fights? Sanji's fight took two, maybe three, chapters, Usopp's fight took about the same, and Zoro's fight will essentially finished in one chapter. Now, it seems like Chopper's fight will end quickly since Hogback has got to be weak and no zombies are fighting (at least, it seems like no more zombies will come and fight). Will Luffy's fight be short, too?
The fights are short, so the arc wouldn't be dragged out. Plus, Oda is leaving off awesome filler material. When the battles are animated, the animators can drag out the fights while the episodes can still serve to entertain. I expect Moria V.S. Luffy to be real short, leaving Oz as the main high boss of this arc.