I somewhat feel that Bang's FRKZ change is more a nerf than a buff. The cost of a burst is greater than the cost of 4 seals and 50% meter. In addition to that, it now has a time limit, which is again not helpful. Current FRKZ is stronger in my opinion, even if the backdashes have been changed to the way they once were. Also, if he still get's counterhit during FRKZ dashes (hoping this isn't the case to compensate with the other things), then it's definitely a nerf. Of course, there are many things I don't know, but considering the way I played Bang (I used FRKZ a lot) it will come as a nerf.
On the other hand, Ragna's new Blood Kain is definitely a buff.