The thing is, Sanji tried to face both King and Queen at once and got immediately stomped without any issues. And now we see how Zoro has extreme difficulty against King as well (sure, he still hasn't demonstrated everything but come on, Tatsumaki is a high end move...).
Marco's feat of keeping them at bay for over an hour is truly one of the best high tier feats imo. Nevertheless, I still put King above Marco, the gap is marginal tho.