My users are stating that during standard time and DST the event's time does not change
The event's time of recurring events? Maybe we have missed an update, but the behavior of our large installation is exactly as i described: I added a recurring event for every day starting on march 1 running until end of April at 8am. The generated events are from April 1 to April 24 at 8 am, then starting at March 25 (when our DST started) it switches to 9am until end of April.
But real people couldn't care less.
It depends: in an international setup this makes perfectly sense. It is actually the only possible way, when e.g. three people in three different time-zones work together. These real people don't care about the time-zones the other people are in, but they want to meet in a chat at the same time.
Three paragraphs earlier, you state that the events time did not change. Are you saying, that recurring events did not change, but single events changed their time?
So I am just reporting that I had users complain that their evets mysteriously changed time on March 11