Funny, I always thought WC taught me to use two hands together. One may block while the other hits, but on some occassions you would use two hands together like the Pak Jarn Sau which some believe is an arm break. Also, anytime you wish to control rather than strike I would say you need to use two hands in concert and WC has plenty of control methods if one is open to them. Being a former cop I know I had to utilize control rather than strikes many times.
Of course the simplest response to any type of grab is to hit the opponent if you are able, but there are times when hitting simply is not an option. Then again I was always of the impression that it took more skill to control than to hit..................perhaps those who do not know how to utilize two hands together are unable to use control and maybe are of a lower skill level