After playing around 142 maps in a 10000-map pool, you can probably expect a repeat based on some back-of-the-envelope calculations. After playing 1000 matches, 1 in 10 matches will be a repeat. Having 100k maps will bump the time to first repeat to 447, not a big change. But consecutive repeats are not normal.
I have no QM experience.
If you really want to utilize a map pool, it would probably be better to keep track of some stats of who has played who. Or, you can assign counters to people, so that if person A is at counter 46, and person B is at counter 95, then they will play map 4695/10000. This ensures a more even map sampling without having a huge array of person-map flags. There are better ways of doing it though.