One possible way to explain why SST seems so weak in the hands of MRF and possibly MRB is that both of them had weak (and relatively weak) inner energy. MRF has been explicitly stated that he has too little inner energy to learn any of the 72 shaolin arts. QKDNY could be used against a stronger opponent, but the premise of the skill itself already required you to be very strong in your inner energy.
I'm not so sure about 3rd ed changes, in what context did MRB say that SST wasn't that impressive?