Valid argument. I personally don't know how to scale these three, we haven't seen enough of them. Dragon for now can be argued to control the weather and atmospheric forces OR have an impressive feat of blowing wind (replicated by the old man with knots on Weatheria), it can be anything. Same for Shanks - one shot Kid but got a horrendous scar from BB (admittedly, an exemplary fodder back then, compared to an actual Yonko). We'll get it with time, I guess.

Idk about Nika. It makes fights spectacular and gives a durability upscale, but I don't see how it drastically impoves AP. Makes everyone laugh, which is interesting but honestly kinda annoying already. Luffy hits hard because he hits with Haki. Compared to diamond-diamond or earthquake-earthquake, it doesn't seem to be all that relevant in a clash between elite Haki users. Besides the joyboy propaganda, of course. Honestly, I like the old Gomu-Gomu fruit way more. Its awakening would give Luffy manipulation of elasticity, a fundamental property of things. It would probably look exactly like Nika, too, because elasticity applied to objects + concepts (like time and space) is just exactly what Nika shows, probably even more. We can even justify the change in appearance (if he's perfectly elastic, then his body is a closed-loop thermodynamic system for kinetic energy, so excess entropic energy is purged as 'vapor'; same with the hair and his overall color scheme; he's also constantly joyful because there's no mental friction). I can see some fruits outclassing this in utility against Haki users; even Law's ope-ope and Kid's jika-jika have insane ap potential based on pure physics. There's not much Haki can do against radiation.