Actually, you dont see many Chinese martial arts in MMA because MMA is built around rules and I know as far a Gung-Fu is concerned, many things would not be allowed (ie: gouges, some groin attacks, eye and throat attacks, etc) which would have said person be at a severe disadvantage.
This must be why WC practitioners rule the MMA circuit.
And yes, I did practice it some years ago.
I do not find this very persuasive. The rules apply no matter what the competitor's fighting style is. Are you really wishing to say that Wing Chun would be sweeping the MMA circuit if only they could hit the groin and attack the eyes? I think such an argument concedes a serious deficiency. What if you're in a fight and you aren't able to gouge the eyes? Oops.
A related and more fundamental problem is that with a few exceptions such as judo and muay thai, the traditional Eastern martial arts do very little in the way of training against resisting opponents. If you are a BJJ student, you train by fighting. If you are a judo student, you train by fighting. Same for muay thai. Most others, you train by standing in lines punching and kicking the air or really slow drills to the tune of "he comes in like this, so I go like this, and then he goes like this...."
Firstly, Wing Chun is a style that is designed to kill, a person throws an attack and the WC practitioner just reacts with what feels natural, in an octagon that could mean killing ones opponent - especially from a student who is not well trained enough to move a kill shot to an injure shot (such as a punch to the chin = knock out, as opposed to the same move but lower being a punch to the adams apple = death - very little variance in location, but big variance in outcome).
Secondly, many WC schools do not teach aspects of other arts, or even the full aspect of WC. For instance, WC is full of some anti-grappling moves, but many schools do not touch on this. This is a problem, not just with WC but with many traditional schools.
Thirdly, I have trained by actually fighting in WC. I have gone cross hands full speed with a third level black sash when I was a green sash (which is quite intense) and got a few bruises to show for it. I got a cracked rib when I did not properly block a kick that was thrown my way. I put gloves on and sparred fully against people many levels above myself. I also pitted my WC skills against the skills of BJJ practitioners (some times they won, some times I won); I also injured my shoulder when learning BJJ. If one can find the right instructor one can learn WC as a full contact style (notice I did not say sport).
Fourthly, I have used my WC skills to supplement other MAs that I have studied, such as BJJ, Judo, Akido, MT, Kali, and Army Combatives and vice versa. I have surprised many a person when I get out of submissions using what i know of WC, or when I block their takedowns, or when I get in the mounted position and proceed to decimate their face with a simple lap-da followed by a series of chain punches.
Believe me when I say that WC is a very versatile style and can add lethality to any other style, one only needs to find the right instructor, and luckily my instructors are well versed in many MAs so they know how to adapt WC to the other fighting styles.
Now, I am not saying that WC is the best style ever, nor would I ever say that one style is better than the other, it all depends on the skill of the practitioner. I am saying that WC is not useless, even when pitted against other styles, based on my own experience and the experience of others that I know.
Any way, thats all I have to say about this right now, its getting late here in Kuwait and I have an early day tomorrow.