He beat Lady Shiva, right? I'm actually slightly disappointed that he and Bats and Shiva are supposed to be DC's top martial artists because that means there are no martial artists who can stun people with a shout or walk through walls or the other insane shit legendary martial artists are supposed to be capable of.
Also, I wonder how Bruce keeps his martial arts skills at the top since the vast majority of his opponents are unskilled and untrained gangsters and muggers. A top fighter needs to train with and fight against other top fighters, but Penguin and Two-Face aren't exactly good at hand-to-hand. I guess Killer Croc might count since he's supposed to be a really good wrestler. If you look at how boxers and UFC people train, they regularly visit each other to spar and such. Training is basically their job and it's not even 9-5, more like 7-5. Which would not leave much time for crimefighting and certainly not much energy.
See, I think Batman doesn't train to fight martial artists, he trains to fight run-of-the-mill criminals who are, like I said, enthusiastic but untrained. So it's not really that shocking that he would get his ass handed to him now and again.
And I'd like to know why you think hand-to-hand combat and martial arts are different. Any hand-to-hand system of fighting would necessarily be a martial art. If there's no system behind it then it would just be untrained flailing like kids do on the playground. Note that I consider boxing to be a martial art since it is a coherent fighting system.