I'm never a fan of lists like this because, as noted, they are so subjective, and what starts as debate can end up as pure argument.
Dixon seemed obsessed with martial arts ranking as the defining component of effectiveness as a vigilante, a POV I just can't agree with. Batman and co would drive a sensei insane because they would ignore martial arts in order to get the job done. They'd mix and match like crazy, shifting from karate, to capoeira, to gymnastics, to fisticuffs, to wrestling, to using a ruddy taser, and all within the space of 10 seconds.
Lady Shiva is constantly stated as being the best martial artist (prior to Cassandra being created) with the "out of the picture" Richard Dragon being her superior. And so she takes down Nightwing because he's stupid enough to make a snarky comment about how she doesn't look like much of a threat. Shiva's problem would be that she is a PURE martial artist, she wouldn't be able to get near enough to Dick to be that much of a threat if he didn't want her to (and then he'd hit her with the smoke bombs etc), and that would wear her out because she's not a long form fighter, or an acrobat, she's a martial artist.
Anyway, by the time we're looking at the likes of Bruce Wayne, Dinah Drake and Dick Grayson, they differences between them is so fractional, to 99.9% of the population, they're both like scythes through wheat. Bruce is a hair stronger, Dinah is a hair better trained, Dick is a hair faster. Which will win? Depends on the scenario.