The matchmaker only matches solos with stacks if the queue is already at a longer time than normal, meaning there is not enough solo players of close to the same rank queuing at the same time. Meaning if you took out the possibility of matching with stacks or people further SR away from you, queue times would increase exponentially. For matchmaking algorithms, queue times are never a matter of offsetting anything, that is done in seconds. The amount of time a matchmaker algorithm takes to find a match is defined only by the parameters set for an acceptable match, and the amount of people matching these parameters that are currently queuing. Shrinking these parameters any more would easily double or even quadruple the already increasing queue times.