Well I think those are one in the same. Things become simplified, aka all about planning the dps, because you are able to dps on the move.The reason why KJC is insanely good isn't really about being able to dps on the move. It's about simplification.
The problem with the previous KJC was the cast time increase made it terrible, and looking back I don't know if AV was too strong of a reflect or it was just such a DPS increase relative to the other two choices. Nerfing it was probably unnecessary when they were going to buff KJC anyways. Any kind of increase on the slow would be good for KJC as even when the slow matters, it's still relatively easy to plan out ahead of time. I don't often find myself needing to pop BR because of the KJC slow; if I use BR, I would've used it whether I was slowed or not.