But you don't always get 6B CH. CH 6B mostly happens when the opponent mashes. Which good opponents won't do. I mean, it's good if you get a CH 6B, but it won't happen all the time. Maybe even rarely. Whereas Tsubaki>Hotaru is guaranteed to combo, and is a more "offensive" overhead, since you can do it off a hop when applying pressure and those really throw the opponent off. And I bet it would do more damage than 6B CH. Now, if only JP Hakus show us them optimized mag-efficient combos...
About 6D: I'm sure there are gonna be instances when it's possible to use.