This appears to be a regression. Go to the RHQ server Events tab, History subtab. Try to filter the results, click Go (I tried severity=Error, there were still Warn level messages showing, also tried source filter "sdlkdgld" and there were still 10 pages of results)
filtering is broken on the alert definition subsystem view. (broken in the same way, adding filters does not reduce the number of visible items) - rev2626
rev2667 - fixes for broken pagination and sorting on the event details page;
Fixed, rev2733
This bug was previously known as http://jira.rhq-project.org/browse/RHQ-1331