Surely it’s Brimstone not Rainbow Typhoon that leads into a favourable knockdown situation? I’m sure she can get stuff off Typhoon if she throws you into the corner while being in the corner herself, but that doesn’t happen often. Brimstone damage is much lower than Typhoon obviously (which makes sense if it was supposed to be her oki grab).
I agree powerbomb is the worst command grab across the grapplers, but I’m not sure what you’re suggesting is the best way to go about ‘fixing’ it. I think the game needs more variety, not more homogenisation, and come S3 if some of the command grab loops get toned down suddenly powerbomb isn’t looking so different to the rest. I think they need to find more unique ways to improve and differentiate the characters rather than taking weaker moves and improving their properties. Having said that, I think the best buff powerbomb could get would be to reinstate the EX knee knockdown - the two were clearly designed to work together and the weak range on PB becomes irrelevant in that situation.