People thought Franky was too strong since he could easily take down CP9 members and matched Luffy 1v1. In Robin's case, she was the number 2 of a warlord's crew, second highest bounty, broken df, and easily subdued the whole crew before. Nami was even lumping her with the monster trio for a bit.
Fans care about powerscaling more than the story does. Plenty of characters gets plot buffs so they can match their portrayal. Yamato, like Jinbe, would just be given a weaker enemy than Sanji in the next arc so he's portrayed above her.