Sorry but just doesn't work that way. We were stuck behind a group of about 50 pax all whom seemed to have incorrect documentation and each one took ages to be either processed or rejected. Nothing to do with spikes or multiple arrivals
I assume you mean that you were behind passengers who were being cleared at nearly 0 per hour, in which case you are still in line and will never leave. "Ages" to clear means it took some amount of time, so if 500 of them arrived in a single batch ahead of you would that take A) just the same amount of time before they got to you or B) 10 X as long as it took to deal with 50 of them?
The duration of the backlog is proportional to the number in line. While the total processed per day has a limit, the length of the line depends on the peak arrivals.