Oracle SQL Developer has nice reporting capability to plot charts. To compare IO outliers using db_hist_event_histogram between two periods, I have created couple of reports for quick comparison.
When you click on report, it will prompt you to select database and input event, period one start snap and end snap, period two start and end snap.
Compare IO wait count outliers by %
Compare IO wait count outliers by Value
Compare IO wait time outlier by %
IO latency for all snaps by Day
IO latency for last 24 hours
Download link for report definition file.
PS Current version of SQL developer supports only 5 different colors for pie charts so there is overlap of colors in first 3 charts.