I write this after experiencing several performance issues during deploying approximately 300PCs across school classrooms - Dynamic Greoup Update shouldn't be a global task, that tries to update all dynamic group members at once, as with about 400-500 clients it creates a need to make the cron for the task to be fine-tuned together with client checkin time (originally I had only 5mins for dynamic group update and 30min for checkin, now I had to make it at least 10min for dynamic group update, but set it for 20min to be sure it won't mess up).
For smoother experience the dynamic group update should be BEFORE client checkins or as the #0 step for every client checkin. Also there should be an option to update a particular client/clients across groups manually without the need to launch global dynamic group update.