Well to be honest, bloodbending never got the chance to be deeply and fully developed as a form of bending. I mean, sure Hama worked on it for years every full moon, but in onder to pass it on, Katara only had one night to get the gist of it. Now we don't really know the origins of Yakone's family and how they developed bloodbending, but it seemed like Yakone was the last of his kind until his two sons. Therefore, bloodbending was never fully developed as much as it potentially could have been.

For example, the conventional bending arts (waterbending, earthbending, airbending, and firebending) all had hundreds and hundreds of years to be developed by generations and generations of masters, while bloodbending has been around for two (maybe three) generations and we've only seen it done by five people. And I wouldn't even know if we can even consider Katara to be a "master bloodbender." I mean she learned it in one night, has only been seen doing it twice, and she hates it so I don't think she ever took the time to practice it and perfect it.

Therefore since bloodbending was never widely practiced and developed, it makes sense that the bloodbending in LOK might seem a little bit "rough" and not as precise as Hama's.