Its not even about that imo. His DF powers become manageable with FS competency. This is why Rayleigh probably was able to keep up with him and fight him.
Akainu probably can do the same thing and is the more competent fighter/military strategist, hence why he's Fleet Admiral
This is why I think if he's Luffy's opponent, it's going to be Katakuri 2.0, except Luffy has to actually master FS instead of just learning it.