I've never paid much attention to power scaling, but i'll say this: young Garling got a big fat L on GV -it was just a no-diff one-shot.
If someone wiped the floor with him again, iI'm assuming two possibilities:
- First, Oda simply wanted to show that, the guy was very weak compared to the monsters on the island back then - the difference was simply HUGE.
- After granting him Gorosei status, and after all these years (the guy is now old, and we know what the first rule is, when it comes to old people in shonens), Garling simply became a monster.
It has to look like this, otherwise why introduce him and making him the BOSS of HK's.