I don't know anything about the Black Dragon System.
I did look around on the website a bit. I'm not sure what to think, exactly. It seems like he is trying to make the Chinese Arts into a very mystical and spiritual thing. While I do believe the martial arts can take on a spiritual side for the individual, the way it is done on the website seems forced and overdone to me.
It's not clear exactly what he studied, and I didn't see any mention of who his teachers were. Lineage isn't everything, and if they were people in China I probably wouldn't recognize them anyway, but usually people will list that to show some form of legitimacy. I found it odd that it wasn't listed, or maybe I just missed it somehow.
He listed a number of sets that he teaches, many of which I am not familiar with. That doesn't mean they are not legit, of course. I did notice the Wing CHun sets, and I think Tiger/Crane, and some Tai Chi and Bagua but don't know anything about the rest. I didn't see any clear listing of where the Dao form comes from. It's hard to understand if he is teaching a complete system or systems, or bits and pieces of several. Many of his descriptions of what he does are very vague. Not much real, concrete explanation of what he is doing.
Here is my honest opinion and impression: This man may be a very talented martial artist and instructor. I can't claim a high enough level of expertise to make a judgement on his skills based on a website and a few videos. But given the presentation on the website, with all the mystical stuff and how vague the rest of it is, if this was my first introduction to this teacher, I would probably look elsewhere.
If you have trained with him and you feel the training is good, then stick with him. You have a solid enough background in other arts that you should be able to make a judgement for yourself whether or not you feel the training is beneficial. I just find the presentation and the material to be odd, and at least unusual. Keep in mind: there are MANY MANY MANY different Chinese arts. Some of them are extremely odd and unusual and might fly in the face of what we might otherwise consider to be the "standard and proper" way things are to be done. Tong Bei (White Ape) is a good example. When done well, it looks like a guy running around and spastically throwing his arms out in the middle of having a seizure. Very strange, yet I can understand how it would be difficult to deal with, if you are on the receiving end of it. I think there are many arts in China that we have never yet seen here in the West. What this man is doing might be one of the more rare systems. Like I said, I just find his website presentation odd, and not my cup of tea.