DST is for discussion, and is sort of like "hey this set is viable" thing. If people start trying out those sets, they'll eventually post them in C&C. In theory this is a good thing, to prevent people from posting asstacular sets in C&C and wasting QC's time. Still, some people post sets they haven't tried (against the rules), so the system isn't perfect. Also, megathreads like the new tiering threads usually become flame wars and a place for people to needlessly increase their postcount (pc++), so it has a bad reputation.