I think it would have gone a lot smoother if each half-season was parallel to a volume - kind of like the first season. It was two episodes short of what we have now, but it was perfect.
The first season had things just right. There were some differences here and there, but not too plot changing. The pacing wasn't too slow or too fast.
The second season was trying to follow the second volume. But with what, sixteen episodes? That dragged it out too much and it seemed like they were trying to improvise.
The third season is moving way too fast. The producers listened to the fans - the last people who should be directing something.
I truly think if each half-season were to follow a volume, we would be fine. The first season is a perfect example.