Going by the speed they are processing the applications now, looks like there is one set of officers working on August applications while another set is working on September applications. Simultaneously, some officer(s) may be working on older cases as well.
I guess most september applicants would get DMs by end of this month or beginning of March. In march, they might start taking up October applications.
According to my observation it looks like they received fewer applications in August, September and October. So the queue is not so big compared to previous months. Plus the quota issue at the end of the year made it worse for applicants from the middle-of-the-year - April, May, June and July.
My analysis: April-July is the worst time to apply, especially for June-July applicants. If they do not run out of quota, then you get it on time. But if they do run out, then the processing time drags and this has been true for the May-July applicants.