characters that have abilities that do not compliment or factor into their martial arts, or have powers that make their martial arts largely irrelevant, are not eligible for the tier rankings. For example, Midnighter, Deathstroke and Duke Thomas all have superhuman enhancements that factor directly into (and do not take away from) their martial arts prowess; whereas characters like Superman, Black Lightning and Wonder Woman have powers that, more or less, make their martial arts skill irrelevant most of the time.
with that being said, here's how I'm breaking down the tiers.
SS Tier (God Tier) "martial arts is my superpower." more than a legend, this tier is for fighters that effectively transcend traditional martial arts and have reached a point where their combat ability are effectively metahuman or mystical in status.
S Tier (Legendary Tier) this tier is for characters that have skills beyond reasonable human ability and can reliably tangle with certain metahumans. these fighters are the "meta" of the DC martial arts world, meaning their skills are the stuff of legend that set the bar for martial arts in the DC universe.
A Tier (Master Tier) these individuals have a distinct fighting style and are athletes operating at the peak of human ability. These are masters of their respective martial arts disciplines and can typically produce capable fighters as pupils. from this tier onward guns become nearly irrelevant.
B Tier (Elite Tier) these are exceptional combatants that possess combat skills that are leagues ahead of the average fighter. those in this tier are typically near-peak level athletes, relative to an olympian.
C Tier (Very Good Tier) these are the above-average fighters. typically hardened from experience and can handle most henchmen and street-level threats with no problem. these characters possess above-average physicality and while guns pose a threat, they're not a significant threat.
D Tier (Decent/Upper Brawler Tier) these are typically self-taught or undisciplined fighters who still know how to handle themselves in a fight.