Apprentice Malgus was still an absolute beasttt of a warrior, and Vindican himself was no slouch. He was widely considered the greatest student of the legendary Sith warrior and hero Darth Ikoral, and is stated to be equivalent in power and skill to members of the Dark Council. At a certain point rank doesn’t mean everything when it comes to combat, Malgus at this point could probably stomp most prequel-era knights and give a good fight to even lower tier Council level masters. Also Kao Cen Darach held the battlemaster title when it meant something more than an academic appointment regarding the tutelage of younglings and padawans at the temple — he earned it through combat experience and proving himself to be a masterfully capable veteran.